The Great Ongoing Aviation Thread (general and other)

Miscellaneous and Personal Stuff I Must Share
3483

More on the NOTAM outage last week:

Oops. Darn those IT gremlins.


And getting back to actual General Aviation, rather than aviation in general, there’s this unhappy event:

The article says that about half an hour after takeoff they reported oil pressure problems and 5 minutes later they crashed aways short of the airport they were heading towards.

There are a couple things about this article that don’t quite make sense to me.

  1. From when they took off to when they first reported a problem was a lot longer in time than the rather short distance they seem to have flown. Even allowing for the usual detours light planes have to make operating in/around New York City. That’s just based on the start & end points; I didn’t try to check any of the flight tracking sites to see their actual route.

  2. The divert field was not in the direction I’d expect given where they’d departed from and where they were going. I’d expect them to have been somewhere southwest of JFK, not northeast of it.

The most likely explanation of both these discrepancies is that the given takeoff time is wrong and the problem manifested shortly after takeoff in a northeasterly direction while they were only a few minutes and correspondingly few miles from the takeoff point and coincidentally nearby the airport they then tried to divert into.

Unfortunately the engine quit before they could get there. A night forced landing on much of Long Island is real unlikely to end well; it’s either dense suburb or dense forest with little else to choose from.

3484

I obviously have no idea what actually happened, but it looked to me like the airplane started raising its nose before the wing dropped. My first thought was misdiagnosed engine failure - an engine stopped making power, and they compensated by increasing the angle of attack, leading to the wing dropping and the plane going in. If they tried to pick up the wing with aileron, it could make the problem worse (aileron reversal). Apparently the ATR-72 had a low-speed aileron reversal issue which was compensated for by adding vortex generators in front of the ailerons.

3485

Good thoughts all.

I saw one recreation where overall I wasn’t too impressed with the tone / skill of the vid producer. But it showed the airplane getting quite flat on the approach (IOW too low versus how far out they were), then climbing for a while, then stalling. Assuming that flatness & climb are/were real, not just sloppy workmanship on the vid …

The terrain along the approach path to that runway is a bit misleading and if they weren’t using ILS or an RNAV/VNAV approach for backup and if the runway didn’t have VASI or PAPI for visual help, they might have gotten suckered low. it’s an easy mistake to make. The fact this was a newly opened airport nobody had flown into before didn’t help. The fact it was a nice big runway aligned pretty well with the valley did help. Once recognized, the remedy is easy enough: add enough power to drive back up to the proper slope, then settle back into the proper descent.

An engine failure in a twin, be it large or small, is hard to ignore as the airplane tries pretty darn hard to roll/yaw into the dead engine. If indeed they’d added a bunch of power with both engines running to get back up to the proper slope, or to commence a go-around, and one quit a few seconds later, they might have ended up as you say.

It seems like too much of a newbie mistake, but if they got flat then tried to climb out of that hole without adding power, the result would be getting slow; real slow. And then perhaps stalling. Which pretty well fits the attitude & appearance of speed (or rather lack of speed) in the now-famous mobile phone recording of the crash just before the airplane went out of control.

Perhaps, a bit like the Asiana 777 crash at SFO, they thought the auto-throttles were actively managing thrust to maintain speed when in fact they were not.

Apparently the FO was flying, but she was on the verge of captain upgrade, so not a newbie.


I flew my last trip with an interesting dude who’d flown for the USN, USMC, then USAF Reserve and now the airlines. Unrelated to the Yeti event he commented

The problem with losing situational awareness (SA) is you won’t know you’ve lost it until you find it again.

Which was a very pithy formulation I’d not heard before. That’s a keeper. Like Rumsfeld’s infamous “unknown unknowns”, when you’re out of sync with reality one of the most salient facts is that you don’t know you’re out of sync. Until reality re-intrudes itself, perhaps violently.

In any case, it sucked to be them.

3486

In happier news there’s this:

A test aircraft using a hybrid hydrogen fuel cell plus battery power system for the left engine. With the eventual intent of the powertrain consisting only of a hydrogen fuel cell → electric motor → propeller.

It is early days for electric aviation, but progress is being made by leaps and bounds.

3487

This seems much more viable than all-battery solutions for commuters. The future of green aviation is probably green fuels, not battery-electric except in some niche cases.

3488

That’s a fuel cell so it’s basically still a battery of sorts.

3489

Sorta.

It’s “burning” hydrogen to make electricity. So from there downstream to the propellor it’s the same set of engineering problems as a battery.

But upstream is quite different. A fuel cell itself isn’t heavy like a battery, but it does require tanked hydrogen. In the current state of the art, the hydrogen, even including tankage weight & volume is better than batteries. It can be refueled quickly, whereas batteries charge slowly.

OTOH, a battery charger, even one of industrial size for recharging a regional airliner can hook into the existing electricity generation & distribution infrastructure. Whereas for hydrogen we need to build a complete transport & hydrogen manufacturing system leading back from the aircraft to the airport trucks or tanks to pipelines from wherever the stuff is manufactured. Plus supply of whatever feedstock they use.

Nobody knows which will win. Maybe both.

3490

I can’t see hydrogen winning for commuter flights (assuming we’re talking fights under around an hour). Battery density is enough to barely handle these cases already, and with a little development they’ll do it comfortably. They’re often turboprops anyway, or at least smaller jets like an Embraer 175.

Fuel cells have the problem of low power density. So they end up needing a battery anyway for takeoff and climb. They have decent energy density, but that doesn’t matter so much on a flight where you start descent almost as soon as you reach cruise.

Certainly, we’ll need something like fuel cells for medium and long-haul flight, so it’s worth development. I just expect battery only planes to come first and pretty quickly take over their niche due to the cost and other advantages.

Fully electric airplanes won’t even need a full charge after landing, because they’ll get a significant amount back from regeneration. I expect flaps will be used only as a last resort (and maybe even the friction brakes).

3491

I dunno. Hydrogen fuel cells will provide more range, but compressed hydrogen for a fuel is still pretty iffy and won’t have the range of jet fuel.

For ‘green fuels’ I was thinking more about using renewable energy or biomass to synthesize green fuels in a carbon-neutral way, perhaps even using carbon sequestered from other power plants as part of the input. That’s quite a way into the future, and maybe we’ll come up with something better. In the meantime, I think battery-electric works for some roles like island hopping or primary flight training, and hydrogen fuel cells may have an impact as well. But ultimately, I think air;lines need a high density fuel like kerosene.

The future is unpredictable. Maybe future breakthroughs will change the equation.

3492

I have zero expertise in this stuff, other than reading the trade press every day.

Smart people have differing opinions today of whether hydrogen is practical. But the hard part of hydrogen is not designing 737/A320 sized jets to tank it and use it. The hard part is getting the stuff created and moved into the airplane in volume at a pace that goes with refleeting the bulk of the airline industry. Affordably.

As battery power density goes up, and we gain experience with high power electronics at altitude, it becomes increasingly plausible to size the fuel-burning engines for cruise and use batteries for takeoff, early climb, and engine failure augmentation. Whether those fuel burning engines are turbofans or fuel cells making electricity to turn an electric motor. And separately, whether that fuel is petro-kerosene, artificial synthetic kerosene, or hydrogen.

3493

Another article on the American Airlines 106 runway incursion:

The article sounds like a bunch of excuses.

3494

It reads like someone has an agenda regarding the way in which AA are implementing changes. Regardless of whether the First Officer was distracted by new procedures and a new aircraft, she wasn’t the one driving, and wasn’t the one in command of the “ship”, she was part of a crew that made a mistake together.

Modern commercial aviation has so many safeguards that it is pretty much impossible for a single error to be a problem, so for an event to happen there must be a number of failures, accidents, distractions, etc along the way. Let’s not forget that this error was still ultimately trapped by the Tower controller and possibly the Delta crew simultaneously.

Whether you perceive them as excuses or just contributing factors is up to the reader. Whenever something like this happens there will be a series of events that, taken in isolation, would seem inconsequential but when combined can lead to catastrophe.

3495

My adblocker hates Forbes. Or more accurately, Forbes hates my adblocker. So I can’t / won’t see the article.

It will be interesting to see whether the issues raised in the article are persuasive to the only observer who matters: the FAA.

3496

That is really the nub of every event that makes the news, and for each newsworthy event, hundreds of more minor events that don’t.

3497

I can easily imagine myself in the position of that FO: new airplane, plus a change in procedure that required her to be heads-down during some of the taxi, having to make a PA…

I’m much more dubious about the corporate boilerplate blather from AA:

“Our commitment to safety is unwavering, which is why we regularly update our Aircraft Operating Manuals to ensure they represent the latest and safest information for our pilots,” American said.

‘We regularly update our manuals’ can reflect normal ongoing changes, and it can also represent patchwork and bandaids over bullet holes. Everyone says their commitment to safety is paramount, and they mostly mean it. Until hard choices come around which might mean spending money. So I generally regard PR statements like that as beyond useless.

What I think I do know from my airline experience (I fly private planes now) is that pilots (and ATC) have more and more required verbiage and tasks that require splitting attention. And as we’ve mentioned before, we have a system so packed, so reliant on slim time margins, I can hardly be surprised when things like this happen.

Let’s also acknowledge that despite iPads with airport maps showing you on the taxiway, which are great tools, airport markings really suck. I’ve been doing this for 20 years, and still regularly experience difficulty figuring out where we are sometimes. At big airports there may be multiple, multiple branching taxiways, all out in the middle of huge swaths of open pavement (I’m thinking Dulles). The signage can be confusing, and we’ve made it more and more complex. And the FAA wonders why we have so many incursions and mistakes. Let’s acknowledge that our system’s complexity contributes to this.

3498

I agree.

This is made worse by tasking pilots with passenger announcements that should be done by the crew on the other side of the cockpit door. They’re there for reason. Use them.

In this case it was AA who “updated” their procedures. If a runway layout looks like a treasure map on an iPad then more consideration should be given to the taxi process. That includes the cockpit crew, the tower, and airport visual displays. The time to improve it is before 2 aircraft collide on a runway

3499

Why do some (all) airlines have the pilot addressing the passengers over the intercom? PR? Reassuring nervous travelers? Pilots’ egos? An actual FAA requirement? Something else?

And is there a significant fire risk with hydrogen fuel cells? I’m sure it’s not Hindenburg-level, but still….

3500

AIUI, the only direct regulatory requirement affecting me routinely is that someone, pilot, FA, or computer must make a PA announcement when the seatbelt sign has been turned on. As a separate matter that affects the FAs, there is a regulatory requirement for the safety demo, plus life vest demo if relevant, plus life raft explanation if relevant.

Beyond that we get into a circularity. The airline writes a policy manual. Which they submit to the feds for blessing. Once blessed, it carries the force of law. If the policy manual says “Pilots will greet the people by PA before departure”, then by golly that’s what’s going to happen 99.9% of flights.

Most pilots would be glad to never talk on the PA ever again unless it’s a matter of immediate passenger safety. And even then would rather delegate it if possible.


As to hydrogen. …
It’s inherently leakier than is jet fuel AKA kerosene. OTOH, for a flight from A to B in airplane type X, it’s going to take Y quantity of chemical energy to power the engines that long/far. Whether it’s all hydrogen or it’s all kerosene, if it starts leaking badly and catches fire, i.e. there’s a crash, you’ve got the same amount of chemical energy and hence (roughly) the same size fire.

Maybe hydrogen spreads a little better or burns a little hotter. Maybe not. IANA expert. Leaked kerosene in bulk sits on the ground in large puddles giving off very flammable vapors. Or turns into giant flaming pools producing killing heat until extinguished or burned out. Gaseous hydrogen leaked in bulk immediately rushes skyward, soon to be far from the wreck and survivors, while liquid hydrogen puddles, but evaporates at a great rate then also rushes skyward.

These are believed to be soluble problems with risks no greater than we’re all used to. I think the current emotional content of hydrogen is much larger than that of kerosene. Which emotion will come boiling out in outraged quantity after the first hydrogen-fueled accident.

3501

hydrogen is extremely flammable but is a hydrogen fuel cell flammable?

3502

There’s no fire inside an operating fuel cell, unlike a kerosene-burning turbofan. They do produce high heat and need active cooling. But it’s far less hot than the normal fire inside a turbine or the exhaust of a turbine.

So I’d bet that the risk of a fuel cell setting off a fire if there was a leak in its fuel supply line would be less than the risk of a turbine starting a fire if there was a leak in its fuel supply line.