Category: Flying

Stories about flying planes and helicopters, discussions of technique and teaching.

Flying above 5,000′ cabin altitude

by philg

In our FAA ground school I had to show students a slide reminding them that FAR 91.211 requires oxygen for a pilot exposed to cabin altitudes above 14,000′ (and when flying between 12,500′ and 14,000′ after 30 minutes). They’ll be tested on that. From experience, however, I know that I feel more alert if I keep the (typically shorter) Cirrus flights to 7,500′ and the (sometimes long) Pilatus PC-12 flights to cabin altitude of no more than 5,000′.

“A Medical Look at Hypoxia” by Kevin Ware, a physician and ATP/CFI is an interesting article from a recent Twin&Turbine. The doc/pilot notes that the narrowing of arteries that comes with aging (and an American diet!) makes it tougher for the brain to get sufficient oxygen when starved due to altitude:

In summary, when a pressurized piston or turboprop aircraft is in the high 20 flight levels and operating just as it was designed (cabin altitude of 10,000–12,000 feet), the pilot’s body is only being supplied with half the oxygen available at sea level. This, in turn, triggers the Bohr effect, further decreasing the amount of oxygen available to the brain and heart, which if the pilot is of mature age, are already compromised due to the narrowing of blood vessels. … Given this physiologic reality, is it really safe for pilots with grey hair and some common health issues such as elevated cholesterol, high blood pressure, and possible arterial narrowing, to operate pressurized aircraft at their highest legal altitudes with cabin altitudes? The answer is probably not. But, if the pilot is willing, some steps can be taken to lower the physiologic risk to a more acceptable level, and it involves the use of supplemental oxygen.

Supplemental oxygen is something that needs to be used before hypoxia is present because its effect on the brain is very insidious and makes such recognition of what is occurring, and the logical solutions that would follow, nearly impossible. The best solution to recognizing the gradual onset of hypoxia is to wear a pulse oximeter anytime the cabin altitude is above 5,000 feet and watch the numbers on the dial.

Worth a read if you’re trying to decide if it makes sense to climb up another
4,000′ in a turboprop to save 15 gallons of fuel. Also if you’re trying to decide on whether to pay up for a pressurized plane or rely on supplemental oxygen. The author of this article implies that the typical buyer of a high-performance turbocharged, but not pressurized, piston airplane should be breathing supplemental oxygen for 95 percent of the flights.

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Slide Rule by Nevil Shute

by philg

A reader was kind enough to give me a hardcopy(!) version of Slide Rule by Nevil Shute. It turns out that the popular novelist was an aeronautical engineer during the golden age of aviation. One of the luxuries of getting in on the early days was working with two of the greats: Geoffrey de Havilland and Barnes Wallis, of Dambusters fame.

Shute says that “the halcyon period … died with the second world war when aeroplanes had grown too costly and too complicated for individuals to build or even to operate.” Those are fighting words at Oshkosh and I think that Game Composites refutes this gloomy perspective to some extent (albeit one of the “individuals” had to be a Walmart heir!).

Shute was an airship designer at a time when a government-run operation was building the R101 (crashed and burned due to incompetence, according to Shute) in competition with the R100, a private effort. I still can’t figure out how airships ever worked. The R100 made it to Canada and back, but got kicked up 4,000 fpm in a light thunderstorm. The British airship industry was doomed by the crash of the R101 and improvements in heavier-than-air planes, but I don’t know why anyone thought that it would ever be practical given the power of Nature and the inability of an airship to outrun a storm.

Social norms were different between the Wars. Shute describes a “married woman living apart from her husband, who established herself in the village while her divorce matured.” Her sexual relationship with one of his bachelor test pilots results in an uprising by the “Wives Trades Union of Yorkshire,” upset that they might have to encounter “that woman.” (see Real World Divorce for how things have changed for the better, from a plaintiff’s perspective, in England!) Shute says that he prefers a married-with-children test pilot who will bring back a prototype at the first sign of trouble.

Airship aviation is an indoor/outdoor experience. Crew members are able to walk on top of the ship, move around outside to make repairs while the airship is flying, go to sleep in a cabin, etc. The weather has to be crazy bad before there is anything that could be called “turbulence” to disturb passengers.

The book covers topics that would be familiar today to anyone involved in startups: raising money and growing a business despite a shortage of capital. Shute co-founded an airplane manufacturer called Airspeed Ltd. in 1931 (i.e., during the Great Depression). Despite an industry that grew as fast as hoped, a war that resulted in huge demand from governments around the world, and thousands of airplanes produced and flown away by customers, the company never thrived financially and was eventually absorbed into de Havilland. A cautionary tale for those who today would try to make money on self-driving cars, electric cars, solar power, or any other obviously booming technology. Shute’s Airspeed simply couldn’t make a significant profit in the face of competition from higher-volume manufacturers that kept reducing their unit costs. The Royal Family bought an Airspeed Envoy, but that still wasn’t enough to stave off the competition.

Shute is eventually pushed out (1938), which he says in retrospect was a smart decision: “I would divide the senior executives of the engineering world into two categories, the starters and the runners, the men with a creative instinct who can start a new venture and the men who can run it to make it show a profit. They are very seldom combined in the same person. … I was a starter and useless as a runner…”

So… to Wes: thanks! to everyone else: read Slide Rule if you’re interested in aviation, engineering, or entrepreneurship.

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Aeronautical Decision-Making 101: Runway Length

by philg

If you’re planning on flying the family somewhere for Christmas…

A couple of months ago at our flight school office one of our Private students was slaving away on preflight planning like it was 1970. She was preparing a navigation log of headings and times taking into account forecast wind and magnetic variation. All computations done on an E6B slide rule, of course!

I asked why she was doing this, given that nearly all of the planes in our rental fleet have a panel-mount certified GPS with moving map and, should that fail, we’re in an environment completely covered by Air Traffic Control radar. She explained that her instructor failed the GPS on every cross-country flight and made her do everything old-school. Her day job is engineering so this effort isn’t overtaxing her brain, but will it contribute to practical safety?

I shared with her a text message exchange that I’d had a few days earlier with a rental customer for the Cirrus SR20. The guy holds a Commercial Pilot certificate with Instrument rating. He has 750 hours of flight time.

Background: FAR 121 requires that airline crews that include two professional full-time highly proficient pilots (well, except when I was flying the CRJ!) be able to land within 60 percent of the available runway.

Me: How much fuel do you want in the plane for your flight on Saturday?

Him: Top off, please.

Me: You’re going to fly for six hours? Where are you going?

Him: Albany.

Me: That’s a one-hour flight. The plane cruises faster and lands more smoothly if you’re not right up near the max landing weight of 2900 lbs.

Him: There’s no fuel available at the airport.

Me: There’s no fuel at Albany? The crosswind runway is 7200′!

Him: I’m going to 5B7. I’m taking my son to visit Rensselaer.

Me: That’s a 2670′ runway in “poor” condition with obstacles. The Cirrus needs about 2100′ to land over a 50′ obstacle so you’d be flying your son with less safety margin that what is required for an airline crew and making it more challenging by going in heavy. The A/FD says “TRANSIENT ACFT CALL (518) 596-5947 FOR FIELD CONDS PRIOR TO ARR.”. The airport is unattended. If you blow a tire there, how long before the plane gets back out?

Him: <not convinced that this airport is a bad idea

Me: Incidentally, East Coast Aero Club has a 3000′ runway minimum with a handful of exceptions such as Block Island.

Him: I didn’t know that. It’s too bad. I was thinking of going to South Albany (4B0) instead.

Me: 4B0 is 2853′ with a displaced threshold in both directions, so really more like a 2700′ runway. KALB is 8500′ for the big runway, has fuel cheaper than the reimbursement rate, no fees if you buy a handful of gallons, and is actually a shorter drive to RPI than either 5B7 or 4B0. The FBO at KALB can fix the plane if something goes wrong and have you back in the air two hours later. Why would you want to go to an unattended airport with a short runway instead?

Him: I thought it would be easier than dealing with an FBO.

I still can’t grasp why a high-time-by-GA-standards pilot wouldn’t see the safety advantage of an 8500′ runway in a massive clearing over a 2700′ poor condition runway that is surrounded by trees. Nor can I fathom why someone wouldn’t want the option of support from an FBO that underprices its services (Million Air at Albany is surely not hoping for an influx of piston-powered aircraft tanking up with 20 gallons of 100LL!). There is always the possibility of a tire or spark plug failure.

A passenger would likely have been safer going to Albany with the student pilot (if it were legal) than with this Commercial-IFR guy with an aversion to FBOs.

Maybe as instructors we should take students to some bigger airports and deluxe FBOs to highlight the value offered by both? It’s great that the U.S. has lots of little airports, but it usually doesn’t make safety sense to use them when a big airport is actually closer to the ultimate destination.

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Veterans Day Observed (F-35)

by philg

Today we observe Veterans Day.

In addition to remembering those who died in previous wars, let’s consider our arsenal for the next ones.

The F-35 was used in combat by the US for the first time in September (Reuters story on attacking a ground target in Afghanistan; maybe a drone could have done this?). Wikipedia says that taxpayers began funding this program in 1992 and that the plane first flew in 2000 (prototype) and 2006 (production version). So it was 26 years from the start of development to the first military use, longer than the interval between World War I and World War II.

Comparison: The B-29, the most technologically advanced plane that we had in World War II, was requested by the Air Corps in December 1939, first flew in 1942, and was used in combat in June 1944 (5.5 years after the start of the program).

Should we be happy with Donald Trump for not starting any new wars? Or unhappy with him for not disentangling us from places where we apparently can’t win (or even define “win”)? See “Who Is Winning the War in Afghanistan? Depends on Which One” (nytimes, August 18), for example.

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Veterans Day with a B-29 crew member

by philg

We went to the New England Air Museum today, home of a beautifully restored B-29, and met two former B-29 crew members. One is 92 and one is 94. Both were navigators, which meant a lot of radar work (identifying islands and cities both for navigating and bombing through clouds). Every B-29 crew member endured missions 12-15 hours in length and horrific weather encounters (see “Plowing through the weather in a B-29”).

It is a great museum in general, but it was wonderful to be there on Veterans Day and have a Huey crew chief from Vietnam show us around the Huey, two B-29 crew members show us the B-29, etc.

Sad to think that the World War II veterans will be gone soon.

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Boeing 737 crash is first mass killing by software?

by philg

The Lion Air 610 mystery/tragedy seems to be mostly solved. The Boeing 737 MAX 8 airplane, which uses a de Havilland Comet (1949; also BBC)-style hydro-mechanical flight control system, has a touch of intelligent software layered on top. This NYT article and an Emergency Airworthiness Directive #2018-23-51 explain how the airplane will trim itself into a crazy nose-down attitude in the event of a single angle-of-attack (AOA) sensor going bad.

“At Doomed Flight’s Helm, Pilots May Have Been Overwhelmed in Seconds” (nytimes) explains 

[disabling the system] would not have been a simple matter of pushing a button. Instead, pilots said, Captain Suneja could have braced his feet on the dashboard and yanked the yoke, or control wheel, back with all his strength. Or he could have undertaken a four-step process to shut off power to electric motors in the aircraft’s tail that were wrongly causing the plane’s nose to pitch downward.

Can we consider this the first mass killing by software?

[Background: an airplane wing will suffer an aerodynamic stall, in which the airflow over the top of the wing is no longer smooth, and lose Bernoulli effect lift, if the angle between the relative wind and the wing is too large. This is what limits an airplane’s ability to hover. To generate sufficient lift, the wing has to be within about 12 degrees of level and the wing needs to keep moving. It isn’t possible to fly super slowly at a 45-degree nose-up angle and still have enough lift to remain at the same altitude. The helicopter works by spinning a conventional airfoil so that, even if the fuselage isn’t moving, the wing is still moving rapidly and generating lift.]

What are some alternatives to Boeing’s design, you might ask? The Airbus philosophy, as embodied in the A320 and subsequent airliners, is to turn everything over to the computer(s). Despite holding the stick all the way back, Captain Sully was not able to stall the A320 that landed in the Hudson River. If the fancy computers on an Airbus aren’t getting what they think is good or consistent data from the various sensors, they hand over the machine to the pilot who can look out the window or at the attitude indicators in the cockpit and do something sensible (or panic like a student pilot, as with Air France 447).

Stepping down the food chain, we have the Pilatus PC-12, a Swiss-designed 11-seat turboprop. The plane starts out with a standard light aircraft flight control system. The pilots’ yokes are connected directly to control surfaces via pushrods and cables. On top of this Pilatus has layered a stick shaker to warn pilots that the airplane is nearing a stall and a stick pusher that yanks the yoke forward. The airplane has a great safety record despite being operated into some challenging short runways and being flown, in some cases, by inexperienced pilots.

Instead of Boeing’s single AOA sensor and software to run the trim, the PC-12 has two AOA sensors and two computers. If both sides agree that it is time to go nose-down, then and only then will the stick pusher be engaged. If somehow both sensors and both computers are defective and push inappropriately, a “pusher interrupt” button is always right there on each yoke. From the AFM (“owner’s manual”):

A friend who is a Silicon Valley engineer texted me incredulously “Wouldn’t they do fusion from zillions of sensors?” My response on the FAA certification process:

It is like ISO 9000. Boeing had binders of paperwork and bureaucratic approval for their design, but the design itself may never be scrutinized.

Almost certainly if the B737 had the same system design as the PC-12 all 189 folks aboard Lion Air 610 would have arrived safely at their destination. The worst that would have happened is the pilots being briefly annoyed by a shaking stick and having to hit a checklist.

I’m not sure if this crash can fairly be attributed to a software problem, since the software presumably did function as designed. It seems that we can attribute the crash to a poor system design, but ultimately the plane was crashed into the water by software.

Related:

  • Wikipedia has a good article on the various aircraft flight control system alternatives
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ADS-B should sequence airplanes at nontowered airports?

by philg

I flew the Cirrus recently to Gaithersburg, an airport that supposedly sees only 131 operations per day (airnav). On the flight from Allentown, Pennsylvania to KGAI, the controllers did not even once tell me to look for a nearby plane. I was pretty much alone in the sky at 6,000′.

Things were different within 5 miles of the destination airport. I arrived on a gusty bumpy Tuesday at 1 pm and became the fourth airplane in the pattern as this non-towered airport. I departed behind a Pilatus PC-12. The Pilatus crew waited for a small plane to land before they could depart. I asked a plane on downwind to extend slightly so that I could get out with my IFR clearance (i.e., there were at least four airplanes operating at 5 pm when I departed). Given the active flight school at KGAI and the fact that I have nearly always found myself with company in the traffic pattern there, I question the 131/day number (since there is no control tower, the statistic may not be authoritative).

There is some structure to the traffic pattern at an airport that makes it a bit easier for pilots to identify each other, but self-sequencing is not always successful. AOPA’s Air Safety Institute: “Eighty percent of the midair collisions that occurred during ‘normal’ [not formation or aerobatics] flight activities happened within ten miles of an airport, and 78 percent of the midair collisions that occurred around the traffic pattern happened at nontowered airports.”

Americans have spent billions of dollars over the last twenty years on ADS-B, partly sold as a way to avoid midair collisions. I’m wondering now, though, if ADS-B solves the wrong problem and/or the non-problem of enroute traffic conflicts.

Maybe it was too advanced an idea in the 1990s when ADS-B was conceived (with an implementation date of Jan 1, 2020!), but I wonder if it would make sense for ADS-B gear to sequence airplanes at nontowered airports. Why couldn’t the pilot press a button on the transponder and have the ADS-B software say “You are Number 3 for Runway 32. Number 2 is turning right base. Number 1 is on final”?

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Ideas for flying around New England

by philg

A Swiss surgeon recently came to Boston for a conference. East Coast Aero Club prices are 1/3 to 1/2 what it costs to rent a plane in Switzerland so he decided to spend a week before the conference flying the Cirrus SR20 3-4 hours each day, with periodic cigarette breaks (regrettably the Cirrus is placarded against smoking, thus rendering it less than ideal for a European physician; in the good old days, four-seat GA planes had ashtrays!).

I thought I would share the set of proposed flights in case it is useful to others.

Readers: Let me know if you have other/better ideas!

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Time to plan the Bahamas and Caribbean trip with new AOPA guides

by philg

I think it is time to plan a new Bahamas/Caribbean trip. The last one was in 2003 in a Diamond DA-40 (write-up). Back then I wrote “The bible of Caribbean flying is the Bahamas & Caribbean Pilot’s Guide by John and Betty Obradovich.” This has been taken over by AOPA and split into two hardcopy books ($80/year for the latest versions) and/or two apps ($80/year for updates). They try to get the new versions out on October 15 of each year.

The guides are good on the basic stuff that you’d find in the FAA Chart Supplement (AF/D): runway length, fuel availability, phone numbers. They add information on nearby hotels, restaurants, and activities, plus some overview information on each island. They’re weak on some critical details for planning stops, e.g., what does it actually cost to stop for two nights in a light single-engine plane? Phone numbers are included, but not the email addresses that a pilot trying to plan would likely prefer. As with a lot of other resources in aviation, the guides assume that you already know what you need to know, i.e., that you’ve already decided which airports to visit. If you know that you want to fly the island chain, but aren’t sure where to stop and don’t have time to make dozens of phone calls, it might be better to let an experienced handler such as Air Journey plan the trip ($795) because they’ll know which airports/countries not to stop in. (See “Is it possible to build an app whose job is to use another app?” for how ForeFlight and Garmin Pilot have the same issue.)

[Wishlist for the guides: (1) fee grid for every airport showing quickturn and 2-night stop all-in fees for light singles, light twins, and single-engine turboprop, (2) a section with suggested itineraries for people who don’t know where they want to go. The suggested itineraries would include airports with reasonable fees and nearby pleasant hotels and/or attractions.]

BeechTalk seems to be a great resource for trip planning. Folks there have done everything. I posted a question about an Eastern Caribbean trip and got back a lot of helpful information, the most inspiring of which was this 2018 tale (unfolding in the replies over 6 pages) of flying a Columbia 400 from Texas to Argentina.

[My initial idea for a trip:

Turks and Caicos may get scratched due to $300 in fees for an overnight (or a lot more if on a weekend of after hours!). The 100LL price at MBPV is quite reasonable, though.]

I thought that it would be fun to stop on the way back in Cap Haitien. The AOPA guide says “cattle and people have unrestricted access to the airport”. From a Pilatus pilot: “I have 18 landings in Haiti. In my opinion, going to Cap Haitien would be stupid, very stupid. There is no security for your plane, and not much to see. I’d rather be out of Haiti thinking about going to Haiti, than be in Haiti, worrying about getting out. If you really need Haiti in your logbook, I would consider Jacmel, but I wouldn’t go there either. As I was told before my first flight there ‘Remember that Haiti’s business is poverty’. The last time I was there, I did a short field takeoff on departure [from a super long runway] to get the F### out of there!”

The Caribbean is one of those places where it vaguely does make sense to fly yourself around in a light airplane. There are no highways linking the desired stops!

Related:

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Private Pilot Ground School at MIT in January

by philg

If you’d like to learn what pilots learn, and enjoy the bracing air of a Boston winter, join us in January for MIT Course 16.687. The dates are Jan 22-24, 2019 and it is all-day every-day.

Details: http://philip.greenspun.com/teaching/ground-school/

This is a for-credit class for MIT students, but it is free to non-MITers.

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