The Great Ongoing Aviation Thread (general and other)

Miscellaneous and Personal Stuff I Must Share
4023

Re the Citation crash and hypoxia … it astounds me that this sort of thing can happen, yet it’s happened multiple times (always on private jets, AFAIK). Surely an automated warning system for pressure loss that isn’t otherwise obvious would be simple and inexpensive?

A few sad incidentals that I happened to come across about this flight. There was only one pilot, which probably increased the risk somewhat of hypoxia going undetected. The pilot had an ATP rating and a 737 type rating and was considered very competent. There had been no previous problems with the Citation.

In a strange twist of fate that sounds more like a novel than real life, the owner of the aircraft had lost his first daughter in a scuba diving accident when she was 19, and the woman who perished on the flight was an adopted daughter whom he had adopted when she was 40, because she reminded him so much of his first daughter. By all accounts he and his wife had a close and loving relationship with her and her young child. She, the child, a nanny, and the pilot were the four casualties.

4024

It has happened on a commercial airliner, at least once.

4025

Thanks for that. Of course I now remember watching the Mentour Pilot video about that very incident, but since I have a memory like a sieve, I’d completely forgotten!

4026

@LSLGuy thanks for your informative post. No need to worry about over-explaining, my high interest in aviation is inversely proportional to my low knowledge of how it actually works. Your explanation makes sense, unlike the suggestion I heard on the news that the plane turned around because the auto pilot was pre programmed for the return journey.

4027

There have been close calls on airliners too, where the crew got almost too stupid to reset the autopilot for a straight descent, which is just a couple of knob twists, and button pushes. Once you realize what the problem is and what the solution(s) are. Anyhow sometimes they, or somebody else on the radio, realizes what’s going on and the day is saved.

There are warning systems.

But they can have latent failures where the detector switch is stuck and the alarm never sounds. They’re kinda hard to test in full fidelity except by depressurizing the aircraft at altitude & seeing if they work. So failures may exist unnoticed for years in a particular jet. Until it’s needed and doesn’t work. Surprise!

Many ways for pilot emergency oxygen systems to appear to be at the ready yet fail upon attempted use. That’s another latent issue. Pre-flight testing can uncover some/most of those, but not everyone is as diligent about that as they might be. Post COVID it’s worse in some quarters. Bizjet owners, and hence pilots, are often very big on cost control. Proper oxygen testing on every single flight would mean replacing expensive oxygen bottles frequently. Testing occasionally (read “only at overhauls”) is much cheaper.

Small cabins depressurize very quickly when all air inputs fail or a hole develops. Airliners depressurize much more slowly under the same circumstance just because the total volume of air to leak out the same size hole is so much more. That can be the difference between 5 seconds and 30 seconds to get masks on and configured. Which is huge. Some bizjets, although not this particular flight, cruise much higher than airliners do. Which can cut the required reaction time down to zero or negative. Regulations require one pilot to wear oxygen continuously under those circumstances. I have no personal experience to suggest that’s routinely flouted, but if I was inclined to bet, I’d bet on flouting. Again that’s not relevant to this particular mishap, but extra-high altitude has been in other mishaps.

If an airplane never pressurizes, or pressurizes poorly, and the alarm never sounds or sounds late, there might only be a window of a couple of minutes while the airplane is climbing rapidly during which a pilot could notice they were feeling weird, recognize the implications, decide oxygen was the solution, and get it on & functioning. Any thought to troubleshoot the source of the problem, tell ATC, change altitude or anything else could easily use up 100% of the short remaining non-stupid time they had. Heck if by bad luck the problem matured just as they was busy with some routine piloting task, changing frequencies, updating the computer, or whatever, that might well have delayed recognition by more time than they had left. In this particular case with a single pilot with nobody else there to help, if he starts down the wrong path there’s nobody to correct him. In a two-person crew with this scenario sometimes one pilot goes for oxygen and the other doesn’t immediately . Until reminded by the example sitting next to them.

Lotta ways this gets bad and gets bad quickly. Failures are rare enough that there’s room for a lot of complacency. That complacency is utterly harmless until suddenly it’s utterly fatal.

4028

Thanks very much for the well-informed expert explanation, as always. I’ll just add, with respect to the very relevant item below, that the typical Citation V has a cabin volume of a little more or a little less than 300 cu. ft. depending on model, so about the volume of a small walk-in freezer, which is very small indeed. Back in my consulting days, I and a few of my colleagues sometimes flew private when the commercial connections were awkward or non-existent, and I hated it when the plane was a Citation – I found the damn thing claustrophobic. I much preferred the slower but roomier props, especially the ones with the well-stocked liquor cabinet at the back! :grin:

4029

Here is one of many YouTubes of a Learjet cargo flight Kalitta 66 where both pilots very nearly died from hypoxia. FYI, “Kalitta” is properly spelled with one L and two Ts; you’ll find it’s commonly misspelled the other way too. This short vid contains the whole story and punchline without much background. There are longer more detailed vids on YouTube about this event that you can easily search up by [Kalitta 66].

I’ve watched one hell of a lot of ghastly training films, and seen and heard a lot of scary shit for real. This freezes my blood.

4030

“Unable to control altitude. Unable to control airspeed. Unable to control heading. Other than that, everything A-OK!”

:grimacing:

4031

Hell of a training tool for explaining hypoxia. My question is why didn’t the controllers ask the crew if they were on oxygen?

And I’d like to know if the clip was edited because the 11,000 ft transmission was completely normal. How long does it take to get out of the affects of hypoxia?

4032

Any “Why not?” question becomes hard to answer.

The original controller working the flight had no idea what was going on until real late in the game. It was his controller buddy in the next chair, and some random pilot, who saved the day by recognizing and articulating the problem. Once clued in, the original controller handled the rest well enough.

Controllers’ job is to control, not to fly. Given a problem related to altitude, their first thought is going to be “clear them to descend”. I do not know what training controllers are given in assisting hypoxia situations. Absent anything beyond a couple paragraphs one afternoon back in newbie controller school, most controllers are probably going to respond with a controller-y solution. Out of habit if nothing else.

The controller cannot know if their problem is a pressurization failure, or a pressurization failure and an oxygen failure. Time spent trying to troubleshoot with a crew on the verge of unconsciousness might better be spent getting them to spin down the altitude target & push the “descend” button. Which will have the effect (unless they’re over high terrain) of resolving the situation safely pretty soon as they revive.

Speaking of reviving: On pure O2 your brain comes back about 90% within 2 or 3 breaths; it’s a pretty amazing experience. On mixed O2 + air the recovery is a bunch slower, but still a minute oughta do it. Within a few minutes you should be mostly normal. But IME from doing the altitude chamber a few times for USAF you’re not 100% until tomorrow; the whole experience is a pretty good slam to your system. Being younger & fitter helps.

I recall reading of a similar set-up once involving a 727. The old fat smoker of a Captain became completely unconscious, the middle-aged F/O got thoroughly uselessly stupid, and the young stud F/E saved the day by watching what happened to the other two, figuring out why, and getting on oxygen and driving the descent until the other two recovered. With the FO recovering long before the Captain. It was still a very close call.

4033
4034

It was pretty amazing when we were looking at a colour wheel at (a simulated) 25,000 feet, and then told to put our O2 masks on and go to 100%. We thought we were seeing colours; but when we went to 100%, they just popped! And of course, the insidious thing was that no one knew that anything was wrong.

4035

@PastTense. Interesting find. Thank you. Nothing too revolutionary.

But it does recognize something I’d been wondering about. Each of these gizmos is gonna have a pretty unique cockpit & piloting philosophy. Far more different then is, say, a Piper from a Cessna or a Tesla from a Nissan. So they will be requiring a type rating for each different make and model, at least at first. Perhaps there will be convergent evolution of designs over time, and perhaps there won’t be. We shall see.

But that will increase the amount of time and expense to churn out a new pilot for these machines. They already face a pretty strong bootstrapping problem to get to the scales that make the whole crazy fun idea pay off as a business. This won’t help.

Also, FAA has standardized on the term “powered-lift” (with hyphen) as the generic descriptor akin to “helicopter”, “airplane”, and “blimp”. Which will lead to weird looking sentences like “Hey Bob, look at those three powered-lifts parked over there!”

4036

IHere’s a direct link to the PDF of the proposed rulemaking:

So all powered lift aircraft will require a type certificate, and pilots will need a type rating. That makes sense right now, as they are all so different in flight characteristics and operation.

For now at least it looks like private pilots are out of luck. Focus is going to be on standing up a number of flight instructors, then training commercial IFR pilots to get a type certificate for the craft in question.

Some quick takeaways from skimming the 521 page document:

  • Right now there is no one qualified to teach this other than military pilots who have flown the Osprey. And they won’t be able to build up a cadre of instructors until the first civilian powered lift aircraft are available.

  • They are proposing to make them follow the rules of both aircraft and helicopters, depending on the mode they are in.

  • They propose full commercial certification standards for the aircraft. That’s expensive and will take a long time.

  • They want to use the VFR fuel reserve requiremnets of airplanes (30 mins daytime, 45 minutes night) instead of helicopters (20 mins). That will disqualify or make nearly unusable most electric VTOL designs, which barely have enough endurance to meet the reserve requirement before they go anywhere. They also want the same IFR requirements (be able to fly to an alternate, plus 45 minutes). That’s going to be very difficult to achieve even for fossil fuel powered lift planes, and impossible for electrics with current tech.

  • Icing could be a real problem. The FAA wants the same icing certification as on large aircraft, with specific attention paid to the propellers. I have never seen a quadcopter or any small powered lift aircraft with deicing capabiluty for the numerous small propellers. In winter here, almost all IFR conditions include forecast icing. So that would make these strictly VFR, which wouldn’t work for most commercial transportation roles. They don’t even plan to allow them to operate in moderate to severe icing, as not enough is known about their behaviour in those conditions.

More to come later. In general, this NPRM shows just how far we are from actually seeing powered lift aircraft in commercial operation. So many areas are listed as unknown because of lack of data.

For example, how do powered lift handle icing? What should IFR procedures look like?. What over-water rules should there be (do the things float, or sink?) What does a maintenance schedule look like for an electric VTOL aircraft woth 14 electric motors? What are the inspection requirements?

This puts into perspective those hyperbolic stories in the garbage tech press about some new electric air taxi that is still being designed ‘but will be in service by 2025’ or whatever.

We are certifying a whole new class of aircraft which has very jovel flight characteristics. This will take time. Mistakes will be made, and have to be corrected. Flight test procedures will have to be developed, and I’m guessing the testing period will be long.

4037

Just to be clear, this whole rulemaking applies only to the devices that takeoff & land with lift fans and that cruise with wings. The machines with pure lift fans for takeoff and cruise (overgrown drone quadcopters) are the ones with stupid-short endurances. As opposed to the winged ones which only have very short endurances.

I do agree in general that this is FAA saying “It’s time to grow up boys. Your machines won’t be flying only on sunny days for PR shoots. Make 'em real or go home.”

This is also just the NPRM. IOW the Fed’s wishlist before industry starts howling about stuff being just too hard. Of course Wall Street and their congressional lackeys will weigh in too. So I’d look at this as a first draft before the other side gets their licks in.

Agree completely with your closing comments about this being a long slow slog. Many of the finance types following the industry believe late 2023 and all of 2024 will be The Great Shakeout. This NPRM should hasten that day.

Many fortunes will be lost and a few made. I wish I had the insight to place a big bet with a reasonable expectation of being right.

4038

I think it applies to all of them, doesn’t it? ‘Powered Lift Device’ is pretty broad. It looks to me like they are saying that when you are in a mode where lift is provided by power, you will be treated basically like a helicopter, and when you are in aircraft mode with wings creating lift you’ll be treated like an airplane. Plus any regulations needed for trqnsition, etc.

I haven’t gotten to the part yet where they talk about passive safety, autorotation, etc. That should be interesting, because powered lift devices don’t have any. It’ll be interesting to see how they certify a machine that spends a lot of its time in a mode where a power failure kills everyone on board. I suspect triple redundancy and the ability to lose one or more engines/motors and land safely will be required.

I have no idea how they will deal with icing. No bleed air from turbines, glycol would be heavy and complicated for multi-rotor use, no passive heat available from an IC engine, etc. I suspect it will be something like electrical heating of the blades, if they ever manage icing protection at all.

4039

Nope. At least not as I understand it.

See the very first paragraph of the executive summary at the bottom of pdf document page 5. Under 14 CFR 1 they have defined the magic word “powered-lift” to mean exactly a machine that takes off like a helo and flies on wings like an aircraft and nothing else. That type of vehicle and only that type of vehicle is what the whole document applies to. And right now the V-22 Osprey is the only such operating vehicle. Which of course is not FAA certificated, only military certificated.

Now deeper in the document they go into the airplane-like and helicopter-like features of “powered-lifts” and the ramifications of each. But the document is not applicable at all to the purely rotor-borne machines. As I understand it.


As to anti-icing, there are IFR-certificated commercial airplanes and commercial helicopters that do not have de-ice/anti-ice capability. So the idea that that would be missing from these machines too is not unheard of. For darn sure that lack would have significant implications for safe and reliable flight operations in winter in much of the world.


I’m not really interested enough at this stage of the NPRM process to spend too long poking at 500 pages of FAA bureaucratese typed up in Times New Roman. Especially not without a functioning table of contents. I’ll be happy to discuss anything you come up with as long as it includes a pdf page number ref so I know where to start reading.

It will be very interesting to see industry’s reaction to this. I get a targeted article feed exclusively on AAMs from Aviation Week every couple of days. There will be plenty of analysis (and hand-wringing) soon enough. I’ll share excerpts as I can.

4040

The civilian version seems to be getting close:

4041

They’ve been trying for that thing to get fully certificated and in production for a couple decades now. I sure hope they succeed. It does seem they’re finally on the home stretch.

4042

Quoting the first post on topic for context …

I am surprised that even as of today, 11Jun = 7 days later, there’s no info at NTSB about this. Usually they have a placeholder entry in their accident report database almost immediately