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Autopilot

posted Aug 28, 2013, 8:13 AM by George Finlay   [ updated Aug 29, 2013, 6:59 AM by Nathaniel Cauldwell ]

Been thinking about teaching granddaughter Naomi how to ride a bike. An autopilot would be handy. But we would want to turn it off more and more so Naomi would get more and more comfortable balancing and steering on her own.

Long trips in fast airplanes are mostly flown on autopilot, of course. Relieved of the need to closely monitor attitude, the crew can focus more attention on the big picture. It is easy for crews to become overly reliant on autopilots though, and lax about checking on them. Those errors may have contributed to the July 2013 crash in San Francisco. 


I and the owner of Columbia 400 N1134N often fly as a crew. The pilot flying is responsible for setting and checking the Garmin GFC 700 while the pilot not flying backs him up. We have made our share of mistakes. But fortunately we have caught and corrected them before we generated headlines. Here is a partial list:

Once we have our clearance, we set our initial altitude, load the departure procedure and set the flight director with the convenient "go around" (GA) button for takeoff. This sets the pitch command bar at 7.5 degrees. At full power, which we always use for take off as well as go around, this is a safe and useful initial pitch, to be used until we switch to flight level change (FLC).

Cleared for take off, we will set the heading bug on initial climb heading. On the MMU6.MMU departure procedure for runway 23 at our home airport, that is runway heading to 600 ft, then 210 to 2000 ft, then 160 degrees. Unless we remember to put the flight director in heading mode though, it will stay in its default roll mode. Should we lose the visual horizon early in the climb, that is somewhat useful from a safety standpoint. But it not safe when it puts us immediately off course as it has several times before we realized our mistake and switched to heading mode.

Clear of immediate obstacles and flaps confirmed up, we will switch to navigate mode so the flight director can give us guidance on the departure procedure, and the pilot flying will normally plan to turn on the autopilot and relax his grip on the stick. More than once, we have been distracted by weather or ATC, and forgotten to switch the autopilot on. Unless we double check for the annunciation on the PFD indicating the autopilot has indeed taken control, the PFD can initially look reassuringly normal, until you realize that the commanded climbs and turns are not happening. 

On that 160 heading we are in NY Class B before long, so TRACON issues vectors for the climb to cruise, and often requests best rate, which means FLC with 124 KIAS selected, and back to heading mode. More opportunity for error: we have sometimes forgotten to switch back to heading mode. And sometimes we have remembered that, but then absent-mindedly toggled the autopilot off, intending to simple confirm it is indeed on. 

Once TRACON has us clear of their traffic they typically issue a vector toward our first waypoint and then turn us loose on our own navigation direct to that point. We have sometimes forgotten to select direct before switching back to navigation mode, resulting in big heading changes that may have led TRACON to wonder where we might be off to.

Overall, the GFC 700 excels, keeping the ship on course through the roughest air. There is only one in 34N, and it is has occasionally quit at inconvenient moments. You would think that would motivate us to constantly practice hand flying. But like many pilots, we practice too little. The rust shows especially during the critical descent and approach phases when we find ourselves having to think about what we are doing more than in the early days of our careers, when our skills were sharp.

Status information is prominently displayed at the top of the PFD. Red X's cover over data locations when their sources quit. Loose the AHRS, and the attitude indicator in the top center is replaced by such an X, reminding us to refer to the backup unit in the center of the panel. In such a scenario, the HSI on the PFD remains partially functional, allowing us to follow the CDI.

We have lost the autopilot and found the only missing data to be outside air temperature, which you would not expect to be required information for an autopilot. When this happened, the PFD was otherwise unimpaired, with the flight director still functioning.

On descent we are in the habit of using VS. While FLC is preferred in the climb, where the throttle is typically left wide open, using it on descent leads to delays in starting or changing the rate of descent, since it takes some time for the plane to loose momentum when power is reduced. 

Control wheel steering (CWS) temporarily gives the pilot control without disconnecting the autopilot and it is a convenient way to set vertical speed for the descent, as well as for handling traffic diversions. When it is released with a selected mode other than ROL, the autopilot will steer the plane back to the selected path.

The other method of setting VS and selecting airspeeds for FLC is via the UP/DOWN button on the A/P panel. For large changes in airspeed that can be tedious, especially in turbulence, since the UP/DOWN button is not available on the RediPad.

Finally, back to that Go Around (GA) button mentioned at the beginning: it is a nice labor-saver at that critical moment when DA or MDA is reached with no runway in sight and any help getting safely up and away is appreciated. The pilot flying presses GA which turns the autopilot off, gives him a 7.5 degree pitch up command bar on the FD, and sequences the GPS to the next waypoint in the missed approach procedure. All that is left is to turn the backup fuel pump on, and smoothly apply full power, stowing flaps when clear of immediate obstacles. Very helpful indeed.




Vertical Navigation (VNAV) is handy when we are getting close to our busy home airspace around New York, cruising high in the teens as we usually are, and TRACON gives us a typical descent clearance: "cross 10 miles west of HUO and maintain 7000". Or when cleared for a full RNAV approach with no procedure turns, since the VNV will pick up and adhere to all the step downs.

The one requirement of VNV that took us the longest time to remember is that any manually selected altitude takes precedence. So typically we would be cruising along at 15,000, with 15,000 as our selected altitude, when the voice behind the panel announces "vertical track" and then dutifully flies right through the interception point on that vertical track. Why? Because we have 15,000 ft still selected, and that altitude will always be the limit to our descent, as it should be, when you think about it.

Hypertension

posted Jan 5, 2012, 11:27 AM by George Finlay   [ updated Feb 1, 2012, 5:58 AM by Nathaniel Cauldwell ]

One afternoon recently, during one of those dreaded medical exams, Dr. Barry Zitomer, formerly an Air Force flight surgeon and now my AME, looked up from the scale on his mercury manometer, slipped his stethoscope earpieces out, unwrapped the cuff from my upper arm, frowned and said “156 over 95”.

I knew at once where he was going next. For years he had been warning me my blood pressure was a little high. My habit was to reply that I was not surprised it read high in his office, because he stood between me and the career I love. In the past, he had always given me a chance to relax a while, taken a new reading and satisfied himself that although it was a little high, it was safely below the level at which the FAA required him to withhold issuance of a new pilot’s medical certificate. That level is 155 systolic, 95 distolic.

So this scenario was similar to being pulled over by the highway patrol and told radar clocked you doing 20 mph more than the speed limit. That is the point at which the fines double, at least here in my home state of New Jersey. There is no point in arguing this with either with a patrolman or with an AME So I asked him what he wanted to do next. He said he wanted me to take quinapril for a week, then come back to see him again.

About a week later, after I had dutifully swallowed 40 mg of quinapril daily since our last visit, Dr. Zitomer again looked up from his manometer, smiling this time, and announced "120 over 80".

All well and good, but my compliance soon waned because I felt fatigued most of the time I was on quinapril and when I stood up quickly I often felt lightheaded as though I was working against a G load in the cockpit.

I fly with Dr. Wayne Isom, a heart surgeon at Weill Cornell Medical Center. When he offered the services of his staff and facilities to augment my periodic medical exams, I accepted, of course. They now have CT scans of my heart and surrounding blood vessels taken a year apart. Wayne’s colleague Dr. Len Girardi noticed a 2 mm increase year to year in the diameter of the ascending aorta, from 4.4 cm to 4.6. Aortic root diameter measured 3.6 cm, which is normal for my height, 77 in, (196 cm.). While aortas commonly dilate with age due to deterioration of elastin and collagen, the tough elastic proteins that give the artery its strength and flexibility, a rapidly dilating aorta may eventually dissect -- similar to delamination -- or rupture. A commonly used guideline recommends surgical repair if the rate of dilation exceeds a centimeter per year, or if the diameter increases beyond 5.5 cm for someone of average build, a little more for someone of my size.

Because lowering average blood pressure may help slow the dilation, Dr. Isom referred me to Cornell’s Dr. Mark Pecker, who went over the data his staff collected from a Spacelab ambulatory blood pressure monitor I wore for two days taking readings twice each hour. I had not taken any quinapril in over a month. Activities were typical for me during the data collection, including 2 flights about 3 hours long, as well as driving, walking, exercising, reading, and emailing. I kept notes on what I was doing at each reading, as requested by Dr. Pecker’s staff. 

When they sent me the results I first thought the monitor was not accurate at altitudes much above sea level, because the readings were unexpectedly high during the two routine flights. But the user manual for the monitor says the useful range is from 500 ft below sea level to 15,000 feet above. There were also several high readings when I was doing other things I would not consider alarming -- driving and meeting with a biologist about Savannah River water quality.

Dr. Pecker explained what the data revealed. Pressure normally drops during sleep; my sleeping average was 121/76 mmHg and my awake pressure averaged 148/99. Mean arterial pressure averaged 92 sleeping, 110 awake. And my average pulse pressure, the difference between systolic and diastolic, was 45 sleeping, 50 awake. These differences between awake and sleeping, referred to as dipping, are on the high end of normal.

Like aircraft stability and control systems and like government systems of checks and balances, mammals have an interconnected set of systems that allow variation in response to changes in short term conditions such as emergencies, changes in body position, activity level and dissolved oxygen, while damping variations and maintaining adequate stable pressure in response to changes in long term conditions such as blood volume.

While these controls are not fully understood, some of the functioning has been studied in detail:

The first control system, the renin/angiotensin system, centers on juxtaglomerular apparatus (JGA) located in the kidneys where it can detect the pressure of the blood entering the kidneys as well as changes in the volume of blood exiting the filtering mechanisms in that organ. The JGA receives signals from the macula densa, a group of cells that detects sodium chloride in the fluid extracted from the blood by the kidneys. In response to a sodium decrease, a blood pressure decrease, and/or a decrease in exiting blood volume, the juxtaglomerular cells secrete renin which splits
angiotensinogen found in blood plasma, forming angiotensin I. 

While this peptide has no known biological effect, it can be changed by angiotensin converting enzyme (ACE) to three forms that impact blood pressure through various means, angiotensin II (A II)  and to a lesser extent, III and IV. A II immediately raises blood pressure by constricting blood vessels. It also triggers aldosterone secretion by the adrenal gland and that hormone causes the kidneys to retain more sodium relative to potassium which by osmosis with body cells increases water content of the blood, raising pressure. A II triggers the pituitary to secrete arginine vasopressin (AVP) which directly decreases the amount of water secreted into urine by the kidneys, increasing water content in the blood, raising pressure.

Dr. Pecker  rechecked my plasma renal activity which Dr. John Laraugh had found at 2.24 ng/mL/hr in 2008. This normal value indicates that an ACE inhibitor like quinapril would be expected to lower overall pressure, which might make it uncomfortably low in some scenarios.


A second pressure control system involves pressure sensors in the circulatory system referred to as baroreceptors . Those located in the aortic arch and carotid arteries are specialized to sense increases in pressure and send signals to the medulla which then controls the rate and strength of heart contractions. Those located in the vena cava and pulmonary veins are sensitive to decreases in volume, which links into the first system by stimulating alderstone secretion by the adrenal gland.

A third control system is based around norepinephrine/epinephrine (aka adrenaline) and is what people are thinking of when they say a situation raises their blood pressure. To rapidly increase the organism’s ability to respond to an approaching challenge, whether that be the approach of a saber-toothed tiger in the old days or perhaps a critical presentation these days, adrenaline secreted by the adrenal gland quickly opens airways to maximize respiration and increase heart rate and contraction strength, and constricts blood vessels to increase perfusion of body cells, while it releases increased glucose and fatty acids into the blood to provide fuel.

With my normal sleeping pressure and significant spikes during my work day, Dr. Pecker suggested drug therapy aimed at the norepinephrine/epinephrine control system might be a worthwhile experiment, targeting the higher pressures seen when I am reacting -- perhaps overreacting -- to stimuli.

Many cells contain receptors triggered specifically by epinephrine. A drug that selectively blocks receptors in cells that control quick constriction of blood vessels and/or output of heart, with a minimum of other impacts would be ideal.

Dr. Pecker is focusing on drugs that block one or more of the three beta receptors, not the other main class, alpha receptors. In that group there are currently drugs that focus on beta 1 receptors, which tend to target heart and vascular functioning more specifically. He recommended starting with nebivolol hydrochloride (CAS No.152520-56-4) marketed in the US by Forest Labs and Mylan Labs as Bystolic. I went home with enough samples of 5 mg Bystolic tablets to keep me supplied until a scheduled follow up with Dr. Pecker, instructed to take one per day. 

A study of drug-drug interaction with warfarin (CAS No. 81-81-2) in 12 healthy adult volunteers showed no impact on the effect of either nebivolol or warfarin. I take 10 mg daily of warfarin after suffering deep vein thrombosis and pulmonary embolism in the last decade. (see article “Pulmonary Embolism” on this site.)
​ 
According to DailyMed, a website with information about marketed drugs maintained by the U.S. National Library of Medicine (NLM), the active isomer is d-nebivolol. It reaches peak plasma concentration in most people about 1.5 hours after being taken orally and has a half-life of about 12 hours.  

​Multiple large scale double blind trials have shown nebivolol to be effective at reducing blood pressure in adults with mild or moderate hypertension. Effect was uniform across age and gender subgroups, uniform over the 24 hour dosing period, and observed within two weeks of the start of treatment.

Ice Repellent Airframes?

posted Apr 19, 2011, 1:57 PM by George Finlay   [ updated Oct 8, 2011, 11:17 AM by Nathaniel Cauldwell ]

Building on earlier research, a team led by Dr. Joanna Aizenberg at Harvard has come up with high resolution high speed video lab data that suggest ice-free airframes may be attainable by mimicking a natural design. 
Aizenberg ACSNano November 2010

They developed textured materials that remain ice free when exposed to supercooled liquid water droplets falling from a height of 10 cm. The droplets bounce off quickly while they are still liquid and before they have time to crystallize and adhere. Of course the velocity reached by these droplets is a far cry from aircraft speeds. 

In a phone conference March 9, 2011, Christopher Dumont and James Riley from the icing project team at the FAA Technical Center in Atlantic City, NJ, suggested that Dr. Aizenberg's team explore working with researchers at Cox and Company. Cox has long experience testing anti-icing technology, and a small wind tunnel ideally suited to the team's research. 

This month, the team is beginning to make plans for wind tunnel testing at the Cox LeClerc Icing Research Facility run by Dr. Kamel Al-Khalil in Plainview NY.

Researchers have already figured out how to duplicate some natural non-wetting surfaces like those on lotus leaves and water strider legs. The key concept has been revealed to be microscopic texturing in a surface that is already hydrophobic. Textures that minimize contact with water can often keep the strong affinity even very smooth surfaces have for water from overcoming water’s own surface tension. The water beads up and just rolls off the lotus leaves. Water striders walk on water without wetting their legs and drowning.

So far, Aizenberg’s team has been working at such small scales they were able to use little silicon rectangles on which they etched their textures, using a method long been used in the manufacture of microchips. To apply the textures to the test forms used in the Cox facility they will need to find a more efficient way to manufacture larger samples. Companies like 3M are likely to have the capability to produce the materials in the volumes and at the costs that will make them practical for aircraft, should the wind tunnel testing prove successful.

In earlier work, a team led by Dr. Di Gao at the University of Pittsburg used polymer coatings containing microscale particles of silicon to obtain similar ice repellant results. It is conceivable that this method may prove a more efficient way to manufacture and apply the textured coating to airframes. 
Gao Langmuir October 2009

The microscale patterns are truly tiny, and seem unlikely to cause increased drag. The brick and honeycomb patterns that are most promising for example are less than 10 microns wide and less than 3 microns raised off the surface. For comparison, a red blood cell is about 8 microns in diameter.

The team is concerned that their results may not be repeatable with higher velocities and smaller droplet sizes typical of aircraft icing scenarios. They saw what might be an indication of this when droplets at lower temperatures below -25 dC were pinned to the textured surface and froze before they had time to bounce clear. A similar result may be found at higher velocities. Smaller droplets typically encountered in clouds seem likely to require less time to freeze, which may lead them to pin to the surface.

What a leap ahead for aviation if durable coatings could be applied to airframes that were so repulsive to supercooled water that icing were to be entirely prevented. Even if not entirely prevented, if ice were made to slide off easily without elaborate counter measures, flying would be more efficient and safer.  The ice that accumulated at the colder conditions in the Harvard experiments proved to be much less securely attached to the surface, probably thanks to the texture.





To Dublin

posted Apr 17, 2011, 2:48 PM by George Finlay   [ updated May 27, 2011, 4:02 PM by Nathaniel Cauldwell ]

Beginning May 25 and ending May 31, 1999, I transported a lovely old green and white Cessna 180 K, N180BB, with a big Continental O-520 engine from Hayward Air Terminal near Oakland California to Dublin, Ireland. Enjoyed it immensely, and managed to avoid ground looping. There are said to be two kinds of taildragger pilots: those who have ground looped, and those who will. I am pleased to still be in the second category.

The last leg, twelve hours over the desolate and unforgiving north Atlantic, was the most memorable. I got a wake up call at 0400Z, 0130 local time for a 0230 briefing by the FSS at St. John’s, Newfoundland. For my crossing, they had arranged a nearly perfect day, with strong tailwinds and practically no significant clouds. The only flaw in the weather was a disturbance passing north of the field that was kicking up rather frisky breezes. I took off in the dark on Runway 20, with the wind at 260 degrees and 20 knots gusting to 30. Runway 29 would have been some help, but it is closed this summer for resurfacing. On the other hand, if I had to deal with a 20 knot crosswind in a taildragger, I would rather have it on the right. I got off ok, even at 25% over gross, and climbed into the arms of a lovely southwest breeze that carried me and my little craft safely all the way to Ireland.

I had ground speeds around 150 knots in the climb out of St. Johns, with the cold front bearing down on the airport and compressing the distance between the isobars. The crew at the FSS had given me the very thorough briefing typical of the Canadian weather service. I took their advice and flew southeast a little while down at 7000 feet until clear of the broken cloud layers circulating around the low, then turned east and climbed to 10,000 feet on course in smooth air. It wasn’t long before the stratocumulus layer ahead was lit up pink by the sunrise. That is a beautiful and heartwarming sight. I suppose one feels that if the sun still rises, then things are likely to go well. This is a line of thought that is not likely to occur to the average person, rising from their familiar bed to begin their familiar routine. It is more likely to occur to a pilot setting out alone over the ocean, acutely aware that he is entrusting his life to a mechanical device and to the whims of nature.

As the day brightened I saw that the stratocumulus layer below was nearly 100 percent overcast, with only occasional breaks through which glimpses of a forbidding gray ocean were briefly visible. Overhead a thin wispy cirrus layer gradually gave way to clear skies. For the first half of the trip, the ground speed rarely dropped below 160 knots, and the undercast gradually broke up to a scattered layer by 35 degrees west longitude.

My clearance was 48N50W, 50N40W, 51N30W, 52N20W, 52N15W, DOLIP, and then direct to Shannon (EINN), which is 52N08W. I had filed Dublin (EIDW) as an alternate, planning to go on if fuel was not a problem once I got near Shannon. I plugged EINN into the GPS, hit direct, and used that great circle for guidance, not about to zig and zag over the Atlantic to make precise waypoints prescribed by some clerk at Shanwick. As it turned out the waypoints were very close to the great circle.

A transatlantic flight quickly leaves both radar and VHF radio range. This is why HF radios, with their theoretically longer range, are a requirement, along with position reports. The HF radio which tested out ok on the leg from Bangor to St. Johns, turned out to have a very limited range. I was assigned the primary frequency of 5618 with backup 2899. For the first hundred miles of the trip, I could hear fairly clear conversations on 5618. Not understandable, of course, since the temporary installation straps it to the top of the ferry tank behind me with no connection to the audio panel. By the time I needed it for a position report at 50N40W, the frequency had fallen silent, and there was no response from Gander Radio.

The solution was to request relays from airline crews overhead on the air-to-air frequency, 131.8. The conversations often led to other topics like what kind of a Cessna was I, how much fuel did I have on board, what was the ride like way down there, how much did they pay me to do this, etc. But the initial conversation always went something like this:

Me: Any aircraft on 131.8, Cessna N180BB, relay request.
Them: N180BB, Air Canada 869, go ahead with your request.
Me: N180BB POSITION 49N46W 0730Z FL100 ESTIMATING 50N40W @ 0830Z NEXT 51N30W
Them: (readback)
Me: Readback correct.
Them: Let me pass this on to Gander. Call you back in a minute.
Me: Appreciate it.
Them: OK, Gander copies your report.

My position reports were passed on by Canada 3000 311, an Airbus 330; Elite 379, a B757; Air Canada 869, Speedbird 503, a B767; KLM 687, United 971, Speedbird 209, and United 905.

Strapped down to the rails where the rear seats normally are mounted was a temporary fuel tank made of aluminum sheet metal, about 3 feet square, full of 124 US gallons of 100LL. Added to the 84 useable gallons in the wing tanks, with the 12 gallons per hour consumption rate checked on the transcontinental shakedown flight, this bird had the capacity to fly for 14 hours with the required transatlantic 3-hour reserve. Thirteen hours at 130 knots would reach the closest Irish airport, Shannon. As luck would have it, that steady westerly wind shaved two hours off the 14 hours it would have taken to make Dublin, the final destination for this delivery flight, so there was still 5 hours of fuel left at landing.

Managing the fuel flow from ferry tanks is often problematic, and this one was no exception. It was installed by a reputable company, Telford Aviation at Bangor Airport in Maine. However, during the test flight from Bangor to St. John’s Newfoundland, when fuel was supposed to be flowing exclusively from the ferry tank to the engine, the digital fuel flow gauge began to show high and erratic rates of flow. A check of the engine analyzer showed no evidence that the cylinders were being flooded, so I concluded that the fuel flow gauge had lost its senses. A little further on, the gauge on the left wing tank began to show a pronounced decline. This was odd, since the main fuel selector valve, which controls flow from both wing tanks, was in the “off” position. There was also a faintly visible vapor plume streaming back from the vent under the left wing tank that I happened to notice while checking for signs of ice during a spell in the clouds.

When the engine suddenly began to starve, long before the 60 gallons in the ferry tank should have been depleted, the digital fuel flow gauge was exonerated. Switching the main fuel selector to “BOTH” restored the fuel flow. In a conversation later that evening with Telford, a plausible explanation emerged. The main fuel selector valve leaked in the “OFF” position, permitting the fuel from the ferry tank to flow both ways–toward the carburetor, and up into the wing tanks. As pressure built up in the wing tanks, the left tank began to siphon through the vent. The solution Telford proposed was to draw the wing tanks down substantially before starting the ferry pump, and then monitoring the wing tank gauges to be sure not to overfill them.

During the crossing, I flew for 3 hours on the wing tanks, then switched to the ferry tank with the pump off, and the main fuel selector valve off. Flow stayed at the normal 12 gallons per hour, and both wing tanks continued to show a decline, particularly the left, confirming the leak theory. When I was close enough to Ireland to risk more tampering, I opened the main selector and switched on the ferry pump. Gradually, the wing tank gauges showed a rise, which was encouraging, since I had more confidence in the gravity-feed from the wing tanks than in the pumps required to get the last one-third of the fuel out of the ferry tank.

I imagine pilots who do this all the time become quite expert at sorting out ferry tank problems. One little gadget I had along with me on the recommendation of the old hand who installed the tank was a manual pump to be used to build up pressure over the fuel in the ferry tank. This would help push fuel to the engine in case both ferry pumps failed. The thought of electric failure halting fuel flow was not comforting, but at least I had a tool to deal with it, however awkwardly.

With my three tastless Newfoundland-made sandwiches and my 1.5 liter water bottle, I was prone to Lindberg fantasies, especially since the flight was only a few days after the May 27 anniversary of his daring flight. A message from my one and only GPS about half way across brought Charles to mind when it said “no GPS position.” I kept on my heading, thinking in the worst case, I would eventually sight some part of Ireland, meanwhile marveling at Lindbergh’s chutzpa. After all, he navigated all the way from Long Island, New York, to Paris, with only a wet compass. About 20 minutes later, the GPS found its bearing again, and led me unerringly to Shannon, and then on to Dublin.

I wonder how Charles dealt with the awkward problem of urination on his 33 hour flight? I had along a collapsible plastic canister with some sort of chemical powder in it that was supposed to turn liquids into gel. Didn’t work. Furthermore, there was no reliable way to seal the thing up when it was filled. I managed to dig a plastic bag out that I had stored my wet bathing suit in, and wrapped the canister in that, tying it up tight. That did the trick. But getting your immersion suit and your jeans down and then back up while jammed between the yoke and the ferry tank behind you is no easy task. There were several uncommanded descents when my knees accidentally hit the yoke. Notice I made no mention of underpants. I left them out of my wardrobe to make this operation at least a little less awkward. I wonder how they manage in space?

There are pilots out there who deliver airplanes year round, often two or three times a month, to far off destinations in all kinds of weather. Among them are Hardy Kalitski, Don Ratliff, Ken Dawson, Denny Craig, Margaret Waltz, and the late John Carlson. The trip I describe here would be routine to any of them. If any of them read this, I hope they find I have captured some of the reality of their business.

Links:

Video of sunrise over Atlantic

Route map

An account by Sape Mullender of another transatlantic ferry flight

Emergency Oxygen

posted Apr 17, 2011, 2:47 PM by George Finlay   [ updated Oct 8, 2011, 11:21 AM by Nathaniel Cauldwell ]

Pilots of pressurized aircraft like the Piper Meridian practice switching smoothly to emergency oxygen in case cabin pressure is lost.

Captain Daniel (Boone) Gibson and his crew in the 79th Physiological Training Flight at Andrews Air Force Base in Maryland do a bang-up job educating civilian pilots on this topic. Ordinarily, they work with military pilots. But about once a month they open their altitude chamber and expertise up in full day classes that can be arranged through the FAA in Oklahoma City. Included are in-depth briefings on decompression sickness, hypoxia, trapped gasses, and other ill effects of sudden exposure to high altitude, along with proper use of supplementary oxygen. A closely-supervised ninety minute simulated flight in the chamber exposes trainees to conditions identical to what occurs at an altitude of 25,000 feet in actual flight. Each pilot has his or her own unique set of symptoms to contend with. The controlled environment in the chamber gives flight crews a chance to explore their symptoms safely. In flight, early recognition of symptoms can help crews detect problems with cabin pressure or oxygen systems.

The Piper Meridian, PA46-500TP, is certified for flight up to 30,000 feet. Behind the copilot's seat is a cabinet within reach of the pilot with a mask designed to be put on quickly with one hand – a “quick don”. It is fed from a green 4.25 cubic foot high pressure cylinder designed to withstand 1800 to 2000 lbs/sq. in. The Pilots Operating Handbook (POH) estimates that when fully charged the system has sufficient supply for one individual for 25 minutes at 30,000 feet when used with the mask supplied, a model MC-10 manufactured by In-Eros. A diluter demand regulator included with the mask normally mixes oxygen with cabin air to conserve supply. There is a switch on the mask that can be used to select higher pressure 100 percent oxygen when needed in an emergency. In this position, supply duration is reduced. There is a MIC SELECT switch in the lower left corner of the instrument panel to allow the pilot to select a built-in microphone in the mask. In-Eros also makes a mask that mates with airtight goggles. That is not standard equipment in the Meridian, but it would be a useful upgrade since the cabin might be decompressed to deal with a smoke condition, and that smoke could be so thick or acrid that it would interfer with vision.

The other five seats in the Meridian, including the copilot's position, are provided with less robust solid state oxygen generators, also referred to as sodium chlorate candles. Beneath the copilot's seat is a tray with two masks connected to an oxygen generator thru a clear plastic tube and a lanyard. The tray slides out into the aisle between the copilot's and pilot's seat. Pulling on either mask and the attached lanyards fires a percussion igniter cap to start a chemical reaction between sodium chlorate salt and iron wool, resulting in the release of heat, oxygen, sodium chloride, and ferrous oxide. Once started, the reaction cannot be stopped. The POH estimates the supply is sufficient for fifteen minutes with the use of the continuous flow masks attached to the generators, with rebreather bags that help conserve supply. In the event of failure or exhaustion of the pilot's emergency supply, the copilot's masks can be used by the pilot.

Solid state systems with rebreather bags are less robust because they do not allow for 100 percent oxygen flow, do not provide a tight seal between the mask and the user's face, do not include a microphone, last about half as long as the high pressure pilot's supply, cannot be turned off, and pose some fire risk due to the high temperatures generated by the chemical reaction.

At a typical cruise altitude of 25,000 feet in the Meridian, with a maximum cabin pressure differential of 5.5 psi, cabin pressure is the equivalent of about 8000 feet, which means oxygen partial pressure (pO2) is at about 135mm. Flatlanders in reasonably good health are comfortable under those conditions. A rapid decompression to 25,000 feet quickly reduces pO2 to about 50mm. Along with other possible stresses in a decompression like wind noise, fog, sudden temperature drop, expanding intestinal gasses, possible smoke or fire in the cabin, a decompression can be very distressing, especially for untrained passengers.

If it can be accomplished safely, the crew may wish to initiate an emergency descent to at least 10,000 ft, where the p02 is 100mm and most people will again be comfortable. Often announcing that a descent to an altitude where oxygen will not be needed will help reduce passenger stress.

To make a maximum rate descent in the Meridian, the autopilot is turned off, power is reduced to idle, the nose is pitched up to reduce airspeed to 168 KIAS or lower, the landing gear are extended to provide additional drag, and pitch is adjusted to keep airspeed below 168 KIAS in smooth air, or below 143 KIAS in rough air, to avoid overstressing the airframe. In the simulator, 3000 feet per minute descents were accomplished. In any case, the descent should ideally be completed within the 15 minute endurance of the solid state devices on board.

Dr. Wayne Isom, a heart surgeon and a pilot, suggests that flight crews advise passengers to try to remember to breathe slower and deeper than normal to avoid possible hyperventilation when first going on emergency oxygen. What apparently happens in some cases is that oxygen chemoreceptors in the carotid bodies command unnecessarily fast and deep respirations in response to the sudden decrease in oxygen blood concentration following a decompression. This in turn drives blood CO2 levels lower when they are often already at a proper level. Paradoxically, this negative feedback loop can lower blood oxygen concentration.

To check their own oxygen blood concentrations, flight crews could use battery-powered fingertip pulse oximeters such those made by Nonin, Med Choice, or Checkmate to confirm a blood saturation level of 90 percent or better. However, given the increased workload in a pressurization failure, it is usually more advisable to simply slow one's breathing to prevent hyperventilation and conserve a limited oxygen supply.

Links:
http://www.ineros.com/
http://en.wikipedia.org/wiki/Chemical_oxygen_generator
http://en.wikipedia.org/wiki/Pulse_oximeter
http://www.portablenebs.com/choiceoximeter.htm

Cirrus SR22 vs Columbia 400

posted Apr 17, 2011, 2:45 PM by George Finlay   [ updated Oct 8, 2011, 11:03 AM by Nathaniel Cauldwell ]

Fly a turbocharged Cirrus SR22, as we did last month, and you will see Cessna now has real competition for the turbocharged 400, formerly the Columbia 400. The model dubbed G3 (third generation) is available with factory-installed Tornado Alley twin turbonormalizers with published critical altitudes of 25,000 feet. Sure enough we saw absolutely no drop in the 29.1 inches of manifold pressure (mp) showing at sea level all through our climb to FL230. Furthermore, it was very nice to be able to switch on the factory-installed TKS anti-ice system ahead of a climb through a cloud deck with potential for ice. Cessna does also offer TKS as well as the Kelly electric anti-ice solutions, but only as after-market options, and few C400s have ice protection installed so far.

This was only about a two hour flight in close to ideal conditions, compared to many hours I have spent in C400s all over the country in all kinds of weather. But it was enough to whet my appetite for more, and I look forward to getting requests for advanced training from new owners of these swift little birds. Watch your back, Cessna!

Climbing

We were a little below maximum gross weight of 3400 lbs, the day was a little colder than standard, and we maintained 120 KIAS and 1000 ft. per minute or better all the way up at full power, full rich mixture. Fuel burn was about 34 gallons per hour. We cannot say for sure, but it is reasonable to estimate that we were down about 15 gallons by the time we reached cruise. Of course this was a higher altitude than what would be typical for these airplanes on cross-country trips. According to the Tornado Alley supplement (ref#1), at maximum gross weight on a standard day a full rich climb from sea level to FL230 should take 28.3 minutes, burn 16.8 gallons, and take you 74.8 nautical miles from home. The supplement provides guidance for a slower more economical lean-of-peak climb to 18,000 feet, with full rich mixture settings above that altitude. Those figures say a fuel flow of about 17 gallon per hour will result in 600 feet per minute climb at 130 KIAS, which will take 38 minutes, burn 13.5 gallons, and take you 101 miles from your departure point.

Cruising

The G3 has 92 gallons of useable fuel aboard, and at a typical lean-of-peak cruise setting of 17.6 gallons per hour at a more typical cruise altitude of 12,000 feet on a standard day gets you 186 KTAS, according to the book. Put aside 10 gallons for takeoff and climb, reserve a conservative 18 gallons, that leaves you with a cruise endurance time of 3.5 hours, which gets you a good solid 600 nautical mile range in zero wind. That means lunch in Myrtle Beach on the way to Florida should be possible, which is really all anybody wants from these traveling machines here on the East Coast.

How do those figures stack up against the 400? Pretty well. The TCM TSIO 550-C engine in the 400 is designed to be turbocharged, so it regularly carries manifold pressures above 29 inches, typically 35.5 inches in the climb, so it can reach 12,000 ft a little sooner, burning about the same 34 gallons per hour at a full rich climb setting. A typical cruise setting would be 32 inches of manifold pressure at 2500 rpm for a fuel burn of about 18 gallon per hour which gets you about 195 KTAS at 12,000 feet. Allowing 8 gallons for the faster climb, putting aside the same conservative 18 gallons reserve, the 98 gallons of useable fuel in a 400 gets you a cruise endurance of 4.0 hours and a zero wind range of about 750 nm.

We are using 12,000 feet for the comparison in cruise, although they both have built-in oxygen. It has been our experience that whenever conditions permit, most pilots avoid altitudes that require oxygen, especially when there are passengers aboard. Most people do not like stuff on their face or up their noses. If either manufacturer manages to produce a pressurized model, that will be a marketing advantage.

Best of breed?

They both offer, either as standard or optional equipment, all the amenities you expect in a high-end piston single these days: weather datalink, stormscope, traffic, TAWS, approach plates, airways, flight director, platinum engine, WAAS, air conditioning, electronic checklists.

So what distinguishes one from the other?

The airframe parachute. There is no question this was brilliant marketing and it will be a necessity if Cirrus brings a single-engine jet to market. Score one for the SR22.

Doors. Cirrus has stayed with a slam-to-close design with no positive latch or door closed annunciation. Score one for the 400.

Electrical system. The 400 has two equally robust electrical systems, either of which can handle the full load. This is important on an all-electric airplane. Score one for the 400.

Integrated panel. The SR22 was on the leading edge when it first went to the Avidyne PFD and MFD with the Garmin 430 GPS and the Stec 55X. But it has been superseded by the integrated Gamin G1000 including the superior GFC700 autopilot. Score one for the 400.

Solid construction and fine finish details. Cirrus has improved over the years, but if the G3 were a refrigerator, it would still be a Kenmore compared to the 400 asViking. Score one for the 400.

Columbia cut a corner and installed only one GDU 1042 in the 400. Reversionary mode combines all necessary flight information on one display if you lose either the PFD or MFD. But you are hand flying in the event of such an emergency in the 400, since the displays do not include redundant autopilots. In the SR22 the independent Stec 55X is still available for GPS approaches in the event either Avidyne display fails. Hopefully Cessna will put this high on their fix list, but for now, score one for the SR22.

Factory installed TKS anti-ice. Score one for the SR22.

Engine and track data download. This has been available almost since the very beginning from Cirrus and you know it could be logged in the G1000, but is not yet available. Engine data is useful for diagnosis, and tracking data is useful for training. Score one for the SR22.

Speedbrakes. Both are slippery little birds and there will frequently be times in the SR22 when you will wish you could slow down while you go down. Score one for the 400.

Single power lever. There is a link between the throttle and prop controls that automatically increases RPM with MP. There are many who like this convenience and argue that it is safer in case of a go-around or missed approach, which would require the additional step of moving the prop control full forward in the C400, along with the throttle and mixture controls. Others, like me, miss the extra fine control over engine settings that the blue knob permits. So we will score a tie on this feature.

Features that need improvement in both airplanes. In an effort to clean up the cockpit, both manufacturers have buried their breaker panels, alternate air controls, alternate static controls and parking brakes deep in the pilot side foot well, where they are difficult to use and impossible to reach from the right seat. This is dangerous, and the first one to correct this design flaw will have an advantage.

Follow-up article. Cessna claims their C400 is superior to the SR22 turbo because the turbocharger is more robust than the added-on turbonormalizer on the SR22, and because their airplane carries a type certificate. We may look at those claims in the future. In the meantime, as the turbo SR22s fly more hours, we may see more evidence to prove or disprove that claim.

Links:

Cessna 400 PIM

Cirrus SR22 TN PIM

Cirrus SR22 turbo supplement

Cirrus SR22 G3 wing supplement

Cirrus SR20 Engine Failure

posted Apr 17, 2011, 2:44 PM by George Finlay   [ updated Oct 8, 2011, 11:02 AM by Nathaniel Cauldwell ]

At 1405Z on February 2, 2007, a typically cold day in Goose Bay Labrador (CYYR), three pilots departed together in three new Cirrus SR20s carrying registration numbers N901SR, 806SR and 720SR. They filed for Reykjavik, Iceland (BIRK), 1350 nm east, on the first leg of a delivery flight to Phuket, Thailand. Each plane carried a ferry tank in the back seat with 80 US gallons additional fuel. Fritz Schoeder, a Swiss living in Florida, had the delivery contract. He had subcontracted with pilots Michael Bradford, an American, and Siggy Lehr, a German living in Florida.  It had been equally cold on earlier legs from the Cirrus plant at Duluth MN (KDLH), 1300 nm west. For this leg, Fritz Schoeder flew N901SR, while Michael and Siggy piloted the other two. When an enroute weather briefing reported deteriorating conditions at Reykjavik, the flight of three diverted toward Narsarsuaq (BGBW), about 675 nm from Goose Bay.

They were about 100 nm out when Fritz, flying at 13,000 feet, first reported fluctuations in his oil pressure and temperature. Michael, who had been in the lead plane at 9,000 feet, circled back to trail Fritz with Siggy, in case he could not make BGBW, and at 1729Z Fritz advised ATC at Sondrestrom in Greenland, that he might have to declare an emergency. ATC immediately notified Sondrestrom Rescue Coordination Center.  At first Fritz thought it was a problem with the gauges, but at 1749Z, he declaring the emergency.

By early 2007, the SR20 fleet had already accumulated a record of oil breather tube ice blockages on the Continental IO-360-ES engine, which had led Cirrus to issue a winterization kit and a non-mandatory service bulletin #SB 2X-71-10, dated October 8, 2004. The problem was the location of the tube at the front of the engine, directly in the path of cooling air. There has never been a problem reported in the larger Cirrus SR22, which uses the Continental IO-550-N, with the breather line in the back of the engine.

Water vapor produced as a normal byproduct of combustion is intended to vent through the breather tube. But in extremely cold operating conditions the temperature inside the tubes in the SR20 sometimes stayed below freezing long enough to allow the water vapor to turn to ice, occasionally in sufficient quantity to completely block the tube. The tendency is increased at low power settings typically used to extend range on a ferry flight, which resulted in lower overall engine operating temperatures. Denied an outlet, the water vapor can causes a pressure increase over the oil in the pan, and drive it to break out elsewhere in the system, through the filler cap or dipstick tube, for example. The winterization kit restricted the flow of cooling air by reducing the size of the cowl opening and the service bulletin called for insulating the oil breather line.

Many Atlantic ferry pilots were aware of this problem and elected to install either or both the kit and the sleeve. Michael and Siggy had recommended to Fritz that they install the sleeve. Fritz, perhaps concerned about time and money, declined.

In N901SR, the situation quickly deteriorated. Oil appeared on the windscreen, oil pressure began to drop while oil temperature rose. Eventually the engine lost partial power, and the airplane began to descend. Fritz radioed his wingmen that he was heading for Simiutaq (SI), an NDB now about 50 nm northeast of his position at the mouth of the fiord that leads north toward Narsarsuaq, He said he hoped to be able to make an emergency landing near there if unable to make the field. He said to tell his wife he loved her.

There was a solid undercast which he did not break through until 800 feet AGL, by which time the engine had quit and he reported smoke in the cockpit. He could see land, but could also see it was not practical to land there, so he turned back toward the position he had last reported, 60 38N 46 41W, WSW of SI. By this time his altitude was only a few hundred feet AGL. His last radio transmission was about 1810 Zulu, as a AS350 rescue helicopter was departing Qaqortoq (BGJH) just east of SI. A few minutes later, a second helicopter, an S61, departed Narsarsuaq.  Michael and Siggy descended through the clouds and searched for the plane with the helicopters.

Visibility was good, the sea was calm, winds were light, but there were hundreds of small icebergs in the area, making it difficult to pick out a small white airframe. Siggy finally spotted the wreckage sitting nose down in water so clear and calm he could see the wings intact below the surface. The tail had been destroyed and the left door ripped off. Daylight only lasts about seven hours in that area in February, and it was getting too dark so the two SR20s headed for Narsarsuaq, while the helicopters continued the search. They soon found Fritz’s body near the wreckage, in a survival suit and a life preserver. While the helicopter crew was recovering the body, the rocket in the Cirrus airframe fired, spreading the parachute across the water.

An autopsy performed in Greenland concluded Fritz had drowned, though he also had a broken femur. The damage to the airframe in conjunction with the injury may indicate the plane struck one of the small icebergs while ditching. The airplane was not recovered.

Michael is now flying a Lear and Siggy is now an airline pilot. On May 24, 2007, Cirrus made the oil breather tube insulation mandatory in SB 2X-71-10 R1.

Links:

Map of accident area

Service Bulletin

Oil loss report in 2004

Accident report

Single Engine Jets

posted Apr 17, 2011, 2:42 PM by George Finlay   [ updated Oct 8, 2011, 11:04 AM by Nathaniel Cauldwell ]

Tim Slifkin hit a bird at 6000 feet, over the Hudson River. It was night, and he was on his way back to Morristown NJ from Nantucket MA in a Mooney cruising at about 140 knots, The windscreen cracked on the right side but held together. The first-time passenger sitting on the right was startled, but reassured by the pilot’s calm demeanor. Fifteen minutes later, they landed at Morristown. An examination of the airframe revealed signs the bird had been sliced by the prop, glanced off the engine cowling, and then off the windscreen. Feather samples were sent to Rutgers University, where the bird was identified as a Canada Goose (Branta Canadensis). Adults have a typical wing span of about five feet, and weigh about fifteen pounds.

While you currently see single-engine turboprops like the Pilatus PC-12 in passenger charters, you do not see single-engine jets.  One major reason may be FOD, foreign object damage. Air entering the Pratt and Whitney PT6 on the Pilatus must pass through a screen and make a 180 degree turn to enter from the rear. This reverse-flow design protects the delicate turbine blades from birds, ice, and other objects that can be sucked into a conventional jet or turbofan engine, where reverse flow is not an option.

As part of the certification process for aviation jet engines, four pound chickens, or reasonable facsimiles, are fired into the engines from air cannons at 180 knots to simulate bird strikes. Contrary to popular belief, an engine does not need to keep on producing power after such abuse. It simply needs to survive long enough for an orderly shutdown. But that is not good enough if the airframe does not come with a backup engine.

There are two companies working on single-engine personal jets, Cirrus and Diamond, both using the Williams FJ33 engine. There is also the PiperJet, planned around the Williams FJ44-3. But I do not think Piper will survive to build that airplane. (More on that subject in a later post.)

On the Cirrus version the engine is mounted on empennage, with the intake just behind the cabin and the thrust nozzle between two stabilizers in a V-tail. The Diamond uses two intakes mounted to the left and right of the cabin, just above the wing. The engine is integrated in the empennage, with the single thrust nozzle mounted on the bottom.

In 2000, Sam Williams, founder of Williams International, manufacturers of the FJ33, along with well-known aircraft designer Burt Rutan, were granted U.S. patent no. 6089504 on an airframe design that attempts to address single-engine jet FOD. The basic idea is to protect the intake by placing it close to the fuselage and behind a forebody (the cabin) where large objects like birds are less likely to be able to reach. Reached by email, Mike Van Staagen, Vice President for Advanced Development at Cirrus stated categorically that this patent was not used in the design of the Cirrus Jet. However, to the untrained eye, the intake on the Cirrus Jet does appear to be protected to some extent by its position behind the cabin, particularly at the high angle of attack required at takeoff.

The question remains how Cirrus and Diamond plan to address the overall issue of FOD, including bird strikes, and damage or malfunctions caused by ingestion of other foreign matter including hail, rain and ice; also other causes of compressor stalls and flameouts in other turbine engine installations, including crosswinds and the sideslips that pilots are prone to use to deal with them.

Pilots familiar with the Boeing 727 know that engine #2, which has an intake with an S-turn, is more prone to compressor stalls during takeoffs in crosswinds than either #1 or #3, with straight intakes. High crosswind components across the #2 intake disrupt the airflow into the intake, where it is already disturbed by the turn. This tends to lead to variations in the pressure field created by the compressor blades. Those variations can ripple through the engine and in extreme cases cause compressor surge and flameout.

Turbine designs include features designed to help minimize compressor stalls. All utilize bleed valves to relieve excess pressure and some have a system for changing the angle of the stator vanes, which are fixed to the engine body and are not part of the turbine, to help increase air pressure in case of disrupted airflow through the intake.

All turbine operating instructions call for igniters, normally switched to OFF or AUTO for normal operation, to be turned ON for takeoff and for any other situation where engine failure would be particular troublesome or something might possibly interfere with combustion, as when penetrating heavy rain or turbulence. Provided one has enough altitude, restarting a piston-driven propeller airplane is a routine operation. Restarting a turbine in which combustion has ceased is not routine or quick and therefore requires significantly more altitude than what is needed to restart a piston engine. A restart is not an option when an engine fails on takeoff in any airplane. Turbines and turbofans are at higher risk of engine failure on takeoff due their vulnerability to ingested foreign objects and crosswinds. Up until now, except for the injector seats employed in single-engine military jets, the only acceptable solution to the risk has been to install a minimum of two turbine engines, either one of which can supply sufficient thrust for a successful takeoff.

We need to know more about what Cirrus and Diamond are planning to do to deal with this issue.

Links:

Video of bird strike

Sam’s and Burt’s patent

Oh Lord Won't You Buy Me a Mercedes Benz

posted Apr 17, 2011, 2:41 PM by George Finlay   [ updated Apr 17, 2011, 2:42 PM by Nathaniel Cauldwell ]

I recommended that a client sell his airplane last week, but he has not taken that advice.

A green private pilot with an instrument rating that is barely wet, I had agreed to work with him on a transition into a single turboprop. He had already selected not only the model he wanted, but the exact bird, a 2002 Piper Meridian, PA46-500TP.

The first time he ignored my advice was when he refused professional help in the purchasing process. Had he accepted that help, he might have realized that a turboprop is vastly more airplane than required by his flying needs. Failing that, he might have been steered to a more capable model. But failing that, he would very likely have been steered away from the particular plane he bought, which was overpriced by at least ten percent.

He and I had worked together already for a long time, first on his instrument rating, then on his transition into a faster single-engine piston airplane. So I knew his penny-wise, pound-foolish weaknesses. The die was cast when a friend recently bought a turboprop, and he needed to make amends. However the friend has the flying skills and financial resources that allow him to easily handle a Socata TBM, the model in the middle of the turboprop market, between the Meridian and the Pilatus 12.

When it became clear that he was going to buy the Meridian, I told him it was an impractical decision, but agreed to train him. We took the ground and simulator training course at SimCom together. In the simulator, he proved that he needed more work before he would be competent in an essential skill for this and any other airplane — hand-flying approaches in the clouds. But I was resolved to fly with him as long as it took to reach competency. We flew the airplane home together and he began making immediate plans for long flights with passengers. I began to realize that his goal was to log the minimum hours that would permit him to solo. I became alarmed when I realized that we were rapidly approaching those mimimum hours. When I work with a candidate for an instrument rating or a transition, I can decide when a pilot can safely advance to his goal. But when the goal is defined only in terms of logged hours, I need to rely exclusively on the pilot’s agreement with my judgment of his abilities. 

On one of our flights together with passengers, an occasion arose that allowed me safely to give him a clear view of how much he had to learn. We were being vectored to an ILS approach when the glideslope indicator on his electronic HSI failed. The ceiling was high enough, and the final approach course was free enough of nearby obstacles, so I asked him to hand-fly the approach using the backup glideslope. It was a wild ride, accomplished only with much coaching. But in conversations afterward, he focused on the possible causes of the instrument failure rather than on the need for more partial panel training.

Had he been willing to concede he needed put off the goal of piloting the airplane solo for the foreseeable future, and resolve to fly it only with me or other competent co-pilot, then I would have been willing to continue training him. But with no sign of that concession, and with the time rapidly approaching when I would have no control over the operation of his airplane, I recommended he sell it.


Act As If

posted Apr 17, 2011, 2:41 PM by George Finlay   [ updated Apr 17, 2011, 2:41 PM by Nathaniel Cauldwell ]

Let’s suppose you are involved in a business that involved frequent trips to locations less than 1000 nm apart, typically by yourself, but sometimes with up to three colleagues. Let’s also say those destinations are often closer to smaller airports that do not have scheduled service.

You might benefit by setting up an air service for your business. If you only use your airplane(s) to transport people directly involved in your business, and do not offer the service to the general public, your operation would fall under the less stringent FAR Part 91 requirements. Even so, you would be well advised to act as if it were regulated by the more stringent rules in Part 135 or 121.

To maintain a consistently high level of safety, Part 121 and 135 operations are carefully designed and managed. Professionals specify and acquire suitable aircraft, set up thorough maintenance procedures, design appropriate operational standards, and carefully train and supervise pilots..

Preliminary 2007 aviation accident data released last week by the NTSB continue to show Part 135 and 121 operations are substantially safer than Part 91..

Scheduled Part 121 operations logged a total of 18,700,000 flight hours, with 24 accidents, no fatalities. For non-scheduled Part 121, the totals were 605,000 hours with 2 accidents, one fatality..

Part 135 commuter operations logged 302,000 hours, 3 accidents, no fatalities; for on-demand Part 135, the totals were 3,668,000 hours, 62 accidents, 43 fatalities..

Part 91 operations logged 23,835,000 hours, 1631 accidents, with 486 fatalities..

When I was a kid living in Valhalla New York, my dad often had business trips to a Lily Tulip paper cup manufacturing plant in Augusta Georgia. That meant getting to La Guardia Airport (KLGA), flying to Atlanta Georgia, and then driving a rented car from there to Augusta. Westchester Airport (KHPN) is just a few miles from where we lived, and Augusta (KAGS) is a serviceable airport too..

Making money in a scheduled Part 121 air service between airport pairs like Westchester and Augusta, about 600 nm apart, would mean setting pricing as high as that small market could bear to pay for shorter travel times due to direct routes and avoidance of the major airports where delays are increasingly common. And that would mean choosing appropriate equipment for that route. Airplanes would need relatively low capacity and efficient operating characteristics. But they would also need to be to be reasonably fast and comfortable. A Gulfstream or Falcon, with fifteen available seats, might be a good choice provided the airplanes could be kept busy. Keeping them busy would probably mean expanding service to other similar nearby markets to allow equipment to be moved easily to accommodate fluctuating passenger loads..

On-demand charter service for a small group of business travelers on a route like this could use smaller equipment like a Hawker or Citation with about six seats, gaining efficiency without significant sacrifices of speed or comfort..

But companies with enough internal demand for flights to and from less popular destinations frequently find they can justify the expense of running their own aviation operations. If Lily Tulip had stayed in business, maybe they would have hired professionals to set up a good tight Part 91 aviation department following FAA guidelines from Part 135 or 121, and then guys like my dad would have had quick safe trips to places like Augusta Georgia..

Next: a look at three single-engine turboprops, the Pilatus 12, Socata TBM 850, and Piper Meridian. We will see if any of them might be suitable for hypothetical 600 nm Lily-Tulip flights from KHPN to KAGS with up to four passengers..

Contact us to find out if an internal aviation operation would make sense for your business. Email info@principiainc.com or call 917-841-2362..

Links:
2007 NTSB Aviation Accident Table

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