The Great Ongoing Aviation Thread (general and other)

Last weekend I went to a local model aircraft show for the first time. It was a brilliant experience - great value for money, lots of enthusiasts keen to share some knowledge with us novices, and some great flying displays.

For one of them the announcer said they would do some aerobatics that wouldn’t be possible in a real plane. He wasn’t kidding - there followed an amazing display, including ‘prop hangs’ just a few feet above ground level, and all sorts of other stunts I can’t describe. The control and trust of the pilots was amazing, especially as they were doing it all with just hands (whereas in a plane you have your feet to deal with the rudder). The power to weight ratio of those machines must have been very high. Which makes sense - weight goes up as the cube of size, does it not? So if these planes were 1:10 to a full size model, they would be a thousandth of the weight? Some of the manoeuvres looked like the G force would kill a human pilot, never mind the airframe.

It also surprised me slightly that basically the same physical designs work at that scale - even a Concorde. Though I guess the control surfaces were relatively larger conpared with full size, in all cases.

Don’t do this:

Sorry, can’t seem to find an embeddable video. It’s worth visiting the page for that.

Someone on Reddit found their ADS-B route:

Gee. Cessna 152, ~12000 feet, warm day, steep mountain pass… what could possibly go wrong?

But hey, shitting your pants isn’t the worst thing that could have happened here.

Holy cow, that’s a sphincter-squeaking video.

It’s not often you encounter single-digit AGL mid-course. :astonished:

Also, shouldn’t that aircraft now be out of service? It had to have suffered out-of-spec G-loads while pulling that recovery pull-up.

Another person dies by “engine ingestion.” Not their fault, but “Boeing” is featured in every story.

Wow. It’s like one of those insane squirrel-suit videos…but in a Cessna!

Thank goodness for ground-effect lift. (I’m mostly joking).

NTSB has released the preliminary report on the 737 Dutch roll incident.

Turns out it was an extremely mild event, registering 0.03 g of lateral oscillation, with a frequency of about 1 cycle per second, for 20 seconds. There was no impact on heading or bank angle. Doubtful the passengers would even be aware, other than routine turbulence. So the media massively inflated this story.

The crew noticed it because the rudder pedals moved with the oscillation, which should not happen. They reported a fault in the yaw damper system via ACARS.

The NTSB noted the aircraft experienced a severe storm on the ground with 75 mph gusts. And that the behavior began a week later, immediately following an A-check.

This was the second flight after the check, with the first flight also reporting a yaw damper issue, that was resolved by resetting error codes.

After the second flight, mechanics found damage to a control rod, bearing, brackets, the rudder, and the standby rudder control unit, even though it was never engaged.

The NTSB is examining all the damaged components, to understand how the damage occurred and if it was related to the weather event.

Fleet-wide inspections, inspections at the Boeing factory, and a review of 737 MAX flight data collected by the FAA, turned up no matching events or issues.

https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/194423/pdf

From another reader:
It sounded like the A-check was scheduled routine maintenance.

It was noted that the 737 doesn’t have a gust lock, but it uses hydraulic pressure to dampen movement due to gusts. So maybe somehow the smaller standby control unit absorbed the gust energy, instead of the main unit.

So one scenario is that the weather introduced a fracture, and then the A-check, which rapidly drives the rudder to the stops to test the control units, caused the cracks in the brackets to break away.

Then during flight, since the standby unit is moving around, it caused the rudder pedals to move and the Dutch roll, in response to the yaw damper.

There is a custom plane built by Wayne Handley called the Turbo Raven that had a higher thrust to weight ration. I saw him at Oskosh take off, hang on the prop, and pull up. The plane had a reverse pitch prop and he would do a loop and land in the same take off foot print. It was really something to see. The plane is now at Evergreen Aviation museum.

75 mph gusts have to be hard on control surfaces.

We’ve discussed here earlier an MD-80 accident where the aircraft failed to rotate and the ensuing high speed abort was doomed to run off the end of the runway at high speed then wrecking the jet. The cause was previous exposure to high winds while parked overnight which bent some linkages and/or broke some hinges in the horizontal tail.

There are published limits for max windspeed exposure for a parked airplane for at least some airplanes. My 737 manual doesn’t list one, but that isn’t really pilot info; that’s maintenance info and I don’t have access to those books and never did. If there is a published windspeed limit, there should be a graded series of inspections to perform based on how severely the limit was exceeded.

All of which presupposes accurate measurement and recording of the actual windspeed the actual airplane was exposed to wherever it was sitting. Which details turned out to be significant in the case of the MD-80 I mentioned. And somebody whose job it is to know these facts, put 2 & 2 together, and not let any airplane in their fleet fly after a high wind exposure without follow-up.

As well, that presupposes the engineering analysis of what to look for where on those inspections is sound and fully takes, time, gust factors, resonances, etc. into account. Predictions, even very carefully considered predictions using the best possible data and best possible science, are inherently just that: predictions. The real world always contains surprises at some level.

Why wouldn’t external gust locks not be installed ahead of bad weather?

Astronaut and test pilot Joe Engle has died:

He was supposed to go to the moon on Apollo 17, but was bumped for geologist Harrison Schmitt. That had to hurt.

Maybe because there is no such device? Remember, it’d have to be a Boeing part number, not just a couple of pieces of wood and a long eyebolt.

Why? Wheel chocks, air starts, ground power, tow hitches, tail stands etc… are not Boeing parts. That was a lot of damage in the example above.

Not a valid comparison. Rest assured there is a Boeing spec on exactly what kind of connector by brand and part number can be connected to an external air or electrical receptacle. Yes those are now standardized industry wide.

A external control lock = gust lock transfers the force that would otherwise move the control surface to the skin of some surrounding fixed aircraft structure. e.g tie an elevator to a horizontal stab or an aileron to the adjacent flaps. Is the skin of that fixed structure there strong enough to take that load? Is the structure underneath the skin strong enough? What sort of resonances happen when they’re tied together? How large does the surface area need to be to spread the load? For something like a rudder, if you secure it using [whatever] at the bottom, who has analyzed the torsional loads within the rudder itself between top and bottom when it’s only restrained at the bottom while the top is trying to twist in the wind? Etc.

Only an engineer at the manufacturer can answer these kinds of questions. For each surface and each aircraft type.

Does Boeing publish drawings for somebody to locally make their own 737 gust locks? Or do they sanction those made by XYZ Corp under some kind of a PMA-like arrangement? I do not know for dead certain, but in all my time in jets I never saw a gust lock on a big jet, nor did I see a pile of unused gust locks sitting around in a maintenance line office. Nor did I ever read of a procedure to apply them, even back in the days when the pilot (and flight engineer) manuals contained a lot more background material so the flight crew could supervise less than fully trained ground crew at austere locations.

My informed, but inconclusive, conclusion is they do not exist.

I can’t think of any events that occurred because of such damage so it’s probably a moot point. I suppose they could carry one in the fly away kit if it was an issue.

I’m always amazed at the number of small plane pilots who don’t bungee all the controls together internally. It allows everything to move a little in the wind without banging the stops.

There was this one.

I think the “gust lock” is just the damping provided by the hydraulic system. This is considered to be enough. If the winds are so strong that it is not enough then the airline should have procedures for parking / storing aircraft appropriately. I know when I used to fly Dash 8s in Tropical Cyclone territory we would occasionally have to fly them out of base to a safe place while a storm passed.

Michael Collins (of Apollo 11) has a real fondness for Engle, as I recall from Collins’ book Carrying the Fire.