The Great Ongoing Aviation Thread (general and other)

Miscellaneous and Personal Stuff I Must Share
4683

A deliberate all gear up landing in a big jet is expected to almost always end happily for the crew. Passengers may have more of an issue with evacuations, and even more so for unnecessary evacuations. Somebody always at least twists an ankle. Good to see this one came out nominally.

I used to fly 757s and still have the books. A quick review says the normal hydraulic extension system is backed up by a separate hydraulic pump and fluid supply. The relevant emergency procedures suggest landing on whichever gear have extended in preference to trying to retract a partial gear situation in favor of an all gear up landing. So we can conclude the malfunction itself caused a complete failure to extend. Having both systems fail independently on all 3 gear seems highly improbable to me. Suggesting a common cause.

757s and older Boeings have 3-position gear levers: [Up], [Off], & [Down]. [Up] and [Down] are self-explanatory. [Off] is selected in flight shortly after retraction completes. It isolates the whole gear system from the hydraulics. The gear are retained in the retracted position by over-center mechanical locks. For landing, the handle is moved to [Down], pressure is applied to the extend side of all the mechanisms, and down comes the gear. Normally.

As an aside, newer Boeings (777 and subsequent plus 737 Max) have a two-position electrical gear switch replacing the old fashioned big heavy mechanical 3-position handle. Internally the same [Off] functionality is implemented by timers & solenoid valves after retraction completes.

There have been failures on various airplanes in the past where the gear lever gets mechanically disconnected from the hydraulic valve it controls. Or the valve itself gets stuck. If this occurs post takeoff in the course of retraction, the handle or valve may be stuck in the up position, holding hydraulic pressure to the upside. That has resulted in the inability to extend the gear by either normal or alternate means, regardless of how the alternate feature works on that airplane type. Turning off the hydraulic system(s) which power the gear might be a possible work-around for that but is not part of the published gear failure procedures. John Wayne might have tried that, but he died a long time ago now.

Something in that general line of thinking is probably the most likely cause for this event. I doubt we’ll ever get much more detail, but it would be interesting to learn about.

4684

Good info; thanks.

Would you not expect a normal NTSB investigation to happen? Intuitively, I’d think that would be warranted, but then I saw this:

While common sense might suggest that a gear-up landing results in “substantial damage” to the aircraft and is a reportable accident, the definition of “substantial damage” actually excludes typical gear-up landing damage.

That article is targeted towards GA pilots, but I presume the same rules apply. No one seems to be injured, and the damage might not count as “substantial” from the NTSB’s perspective. And of course reporting an incident doesn’t necessarily imply an investigation.

4685

I would certainly expect NTSB to be involved from the git-go and to publish a preliminary report within the usual 2-3 weeks. Prelims pretty well amount to a narrative of the clearly obvious facts of the matter. As in “gear would not extend, crew landed, jet damaged, nobody hurt”. It might have something useful to say about the “why” of the failure itself, but probably not.

It’s the full investigations that take a 6-18 months that would delve into the “why” and “lessons learned” of the mishap. That’s where we’d definitely learn something of the original mechanical cause. And I’d be surprised if one of those was run on this event.

That may well be a hull loss simply because the cost to repair the old airframe and engines exceeds the value of a mostly obsolete airplane type. Or it may fly again somewhere, even if not for UPS. Hard to say from this distance. The pix don’t show anything obvious like a bent fuselage or broken wing that would spell certain doom. For darn sure even if it is going to be totaled, one hell of a lot of perfectly good used parts will be scavenged off it first.

4686

Student/instructor killed in spiral crash into house.

Not sure why there was a 3rd person in the plane but she survived. It was a twin engine Piper. Looks like a Seminole. They’re saying a sudden change of speed from 5000 ft. May practicing stall recovery.

4687

Well at least the crew kept it out of MEM. That would have been rude.

4688

Excellent point there @Magiver. I had a similar comment upthread about another gear-up event:

In a more serious vein about the FedEx Chattanooga 757 , I finally read the AP article and watched the vid closely. It appears they took off from CHA, had some sort of gear malfunction promptly after takeoff, and elected to return to that airport. A look at the Official KCHA Airfield Diagram (faa.gov) says the long runway is 7400 feet long.

Given the possibility of sliding a good long ways with zero braking control, I’m not sure I’d have been happy landing on something that short. The process of flaring and touching down softly feeling your way down to the runway at a lower than normal eye height with some power still in suggests you’ll probably land long and maybe a bit fast. You’ll also be less draggy than normal, so even a normal power reduction will leave you faster in the flare than you’re used to. I could easily see touching down 2500-3500 feet down the runway and being happy with that as long as it’s extra smooth. Leaving not too much for stopping. Smarter nt to paint yourself into a corner by starting out with just 7400 feet to work with.

Memphis, Nashville, Atlanta, Charlotte, and even Birmingham are all superior airfields, are probably familiar to the pilots, and are all close enough (and have enough runways) that if they simply headed that general direction while running the gear problem checklist they’d be at that other airport before they finished. Which makes me wonder: “Why did you elect to stay at CHA?”

The AP article mentioned them “circling”, but whether that was them buying time to run checklists, was them trying to burn down fuel, or was simply a reporter trying to explain them making a single hasty traffic pattern & landing ASAP I could not say. But I am now wondering if there was something else going on that caused them to want to land sooner rather than later. Something for which the gear was more of a distractor than a cause for the haste.

Curiouser and curiouser.

4689

Ouch. I watched that vid on a big screen several times. It looked spin-like at first, but by the end it was well nose low and should have been unstalled or getting close to it. I looked carefully for signs of structural damage, but all the big pieces seemed to be there.

In addition to your good idea of stall practice gone wrong here’s another idea …

One of the things they do in light twin training or checkout is Vmc demo / training. Get slowed down to near Vmc at idle or low power, simulating a short final glide to landing. Now do a go-around but with just one throttle. Simulating an engine picked the wrong time to fail to accelerate evenly or even to quit. The point is to learn that that is a VERY bad situation and the smart immediate thing is retard the good engine quickly and recover from all the flailing. Leaving the asymmetric power in and trying to rudder your way out will (generally) not work. Now consider that for most light twins standard approach speed is slower than Vmc. So are standard liftoff speeds. Driving around below Vmc is something done on every takeoff and landing, but something to be handled very, very judiciously and for as short a time as possible.

If that is screwed up enough one can enter a spin. And if you don’t get both engines to idle you’re not going to recover, period, amen. And even then it can take a lot of altitude or may even be impossible for Chuck Yeager. Much less a 22yo CFI who’s (probably) never spun an airplane or exceeded 60 degrees of bank, nor has anyone in the last 6 generations of pilots who taught the person who taught the person who taught the person who … taught our CFI.

An aft CG loading (the passenger) makes the spin recovery problem problem worse.

It looks to me like they were in the process of recovering from the spin (or unstalled Vmc gyration). If they’d had another 2-3000 feet they may well have gotten the rotation stopped and then with enough more altitude recovered from the dive if they could thread the needle between over-G and gross overspeed. Sadly, they had nowhere near that much altitude. Nor would it have been practical to conduct the training high enough to have that altitude to start with.

Damned shame.

4690

Yah, I was thinking CHA wasn’t the best place to land. I didn’t realize the longest runway was 7500 feet. That’s why God made 727’s.

I wonder if they could dig a cowling into the grass (using the rudder) if they got desperate.

I don’t know how easy it is to get out of the cockpit but I’d be thinking of the quickest egress once the plane stops moving.

4691

The 757 ended up fully in the grass. The AP article says “beyond the runway in a safety area”. Comparing the overhead view in Google maps with the pic in the AP article it looks like they landed on runway 20 and ran off the end and perhaps to one side or the other; can’t really say much about lateral.

A 757 with the gear down is a very short-field jet. We ran them into Orange County (KSNA) for years with 5700 ft of runway. Other carriers still do. Gear up is the big unknown. No way to know how far or how well it’ll slide until you try. Plus again landing a long way down the runway trying for a soft touchdown under very weird circumstances.

I’d not be in a crazy rush to jump out after it quits moving. Promptly do the evac / emergency shutdown checklist then leave expeditiously. Make haste slowly for fewer mistakes.

The choices are open the cockpit windows, throw out the shinnying rope, clamber through the awkward window opening, and slide down the rope 15 or 20 feet to the ground. That’s kinda gymnastic and runs the risk of losing your grip and falling and breaking a limb. Now you’re stuck in the shadow of an airplane that might be on fire soon if not already. Oops.

Or step aft to the forward entry or forward galley doors, open one or both, watch the slide(s) deploy for the ~8 seconds that takes, then jump into them. The pic in the AP article shows a deployed forward right galley door slide. The cockpit is at about half the normal height so the slide is about half as steep as normal. Looks like a pretty pleasant playground ride to me. A widebody slide at full steepness from full height is an intimidating thing to consider jumping into. This? Not so much.

4692

On a roll here. Here’s a less successful gear up landing from a couple weeks ago. No injuries, but definitely a total loss with no salvageable parts:

The pilots did however keep it on the runway.

4693

Judging by Russian/Soviet concern for their troops, that page just says “In event of engine issue above 0 AGL: Do svidanya Tovarish”

“The 3 Fs Rule” And as I reminded one of my friends during the reception for her 3rd failed marriage, “The longest sentence in the Enlish languge is ‘I do’.”

4694

Quoting myself from yesterday for context:

Turns out this accident was a year and a couple weeks ago. That’s what I get for skimming web pages laden with distractors.

Here’s the NTSB Prelim Report - Docket WPR22LA353. It was a single pilot operation. The pilot says he lowered the gear and flaps normally, doesn’t recall checking the gear came down, heard no warning horns, noticed no warning lights, and landed with the gear up.

I doubt there will be a more complete investigation and report, but the ~5M question is whether the gear control was found in the up or down position.

Warning systems can fail, and for situations that don’t occur naturally in normal ops, that failure might sit latent for weeks or months unnoticed. In all the jets I’ve flown, you tend to notice the red lights for gear in transit promptly as you move the gear handle although there’s not a formal check that they illuminate on the way to green. And there’s no routine test of the warning horn that, if you do your job right, you’ll never hear in the course of normal ops.

Of course there is a procedural check after final landing configuration is established to look explicitly for handle position and for the expected green lights. Not seeing that and also not hearing the horn would be a huge clue the horn has failed. And also a clue that for whatever combo of reasons you did not put the handle down and/or the gear did not extend.

So this smells to me like either:

  1. The pilot lowered the gear control, there was a failure of the gear to move and a (possibly latent) failure of the red lights and/or warning horn, and they did not check their work before landing.

  2. The pilot never lowered the gear control, there was a (possibly latent) failure of the red lights and warning horn, and they did not check their work before landing.

  3. The pilot never lowered the gear control, there were no failures, the pilot failed to notice or process the red lights and horn sounding, and they did not check their work before landing.

I can’t say which occurred. But IMO Door #1 is by far the least likely possibility and still represents less than stellar operating procedure & technique, despite being the most pilot-favorable interpretation of the three. Oops.

We have all failed to run one or another checklist at one time or another. And that’s with two people available to remember. The usual culprit is something else causes you to be busy right as the usual triggering event for that checklist occurs. By the time you’ve disposed of the distraction, you’re into the next phase where that checklist is (normally) already done. As always with human cognition, noticing or remembering something that happened is easier and more reliable than noticing or remembering something that did not happen.

Single pilot ops are very, very unforgiving of task saturation or of weak habits. Even strong habits are no guarantee of success.

4695

Juan over at the blancolirio YouTube channel is strongly leaning into that as the explanation.

4696

Prior mentions of VMC within this thread for anyone wanting more context on the phenomena. In each case here I’m only citing the first post of a group of back-and-forths on the topic before the thread moved on to the next issue:

And some other threads where VMC made an appearance. Including appearances by Dopers who’ve left us and Doper’s who’ve left the Earth.

The fact VMC keeps getting talked about suggests that pilots failing to recognize and avoid its dangers remains a perennial problem in aviation.

4697

More interesting ferment in the electric VTOL space. This outfit in Austria

has flown their proof of concept prototype

which uses this sort of rotor which has some interesting control capabilities not available from the usual horizontal prop disc. They have some other vids on their channel which show them flying outdoors (the latest test) and also some good explanation of how these rotors work.

They have some other vids on their channel which show them flying outdoors (the latest test) and also some good explanation of hos these rotors work.

4698

Neat idea, but it looks heavy. Their thrust-to-weight ratio is only 2.4. Seems hard to believe it would pay for itself compared to ordinary drone motors. For a quad rotor setup, you’d want at least 2x thrust redundancy, which isn’t going to be possible here.

4699

This was proof of concept model. They’d have to double the propellers if they got the lift/weight numbers needed for efficiency.

And they’ve tried rotary wings before as seen in this video of goofy aircraft.

4700

That 2.4:1 lift:weight goes down to 1.2:1 with 2x redundancy. That doesn’t leave much capacity for a body, or battery, or passenger, or pretty much anything.

They say they have a next-gen version in the works with a 4:1 ratio, but even that isn’t so great. Typical drone motors do a lot better than that (like >10:1).

4701

I too have my doubts it’s a fully practical design no matter how they scale it or tweak it. Supposedly one of its main advantages is quiet operation.

Lots of Euro-stuff is like that. They start from a greenery goal like no noise, or all reusable materials, or whatever and engineer as best they can within that highly social, utterly non-economic goal. An American would laugh all the way to the bank while spraying noise on everyone else. These guys and others like them may have the last laugh however.

The Chinese are way ahead in this biz because they don’t care about greenery or safety. The Americans by contrast are real big on safety. The Chinese lead may not last once the backlash from all the dead people from falling EVTOLs gets added to the mix.

4702

The less charitable view is that the Germans (and Austrians?) are in love with showing off their engineering prowess without much regard to cost, practicality, manufacturability, repairability, or other virtues. Seems to apply to their cars, at least (says an ex-BMW driver).