Air crash of the past

[edyvw]

Originally Posted by Exhaustgases
Having important things like control surfaces operating on hydraulics is just plain stupid. Can you imagine a B-17 in the war days filled with holes, many that flew back to their bases with major parts missing, if they would have had hydraulic controls the tiniest of leaks would have doomed them. All important systems like controls should be triple redundant, hydraulic okay but then back it up with mechanical. Just like the jack screw, it needed 2 of them and a fail safe blocking system, and then a couple of come alongs and attach points so someone could crawl in there and manually adjust the position to get to the nearest base.
I suppose strong springs to center the stabilizer would be a good idea as well.

Astro14 pretty much explained everything.
Take into consideration that air travel still is by far safer than it has ever been before.

 

[Astro14]

I should add that cables for flight controls aren't 100% reliable either.

99.999% maybe, but planes have crashed from failed cables, and from cables that had inadequate tension, leading to insufficient control authority and subsequent crash.

All control systems have exhibited failure modes.

Hydraulics are good, particularly since they enable control power that muscle, even with leverage, cannot provide, which allows larger, faster, and safer, airplanes.

I'll be very interested to see how the 787 flight control architecture performs in long term service.

 

[edyvw]

Originally Posted by Astro14
I should add that cables for flight controls aren't 100% reliable either.

99.999% maybe, but planes have crashed from failed cables, and from cables that had inadequate tension, leading to insufficient control authority and subsequent crash.

All control systems have exhibited failure modes.

Hydraulics are good, particularly since they enable control power that muscle, even with leverage, cannot provide, which allows larger, faster, and safer, airplanes.

I'll be very interested to see how the 787 flight control architecture performs in long term service.

Are you going to move to it?

 

[Astro14]

Not anytime soon.

I'm very happy on the 757/767, which is the dinosaur of our fleet, but a good airplane, with excellent power, solid handling, and a great safety record. As an example, I landed in Eagle, CO a while back, with 31,000 lbs of gas, at 6,500 feet elevation, and had no problem turning off the runway early. Such a great airplane!

The 787 is likely the future of aircraft systems architecture. The carbon fuselage, the on-demand systems, etc. have all delivered an airplane that has huge fuel efficiency and range improvements over existing/conventional airplanes.

 

[4WD]

Customers like them too

 

[PimTac]

Indeed. I prefer being a passenger on a 787 over a 757 or 767. The 787 is quieter.

 

[Astro14]

Originally Posted by PimTac
Indeed. I prefer being a passenger on a 787 over a 757 or 767. The 787 is quieter.


It's a sweet airplane from a passenger perspective. Flown on it a few times, now. Will fly from EWR to SFO as a passenger on it next week (for work).

I'm told it's sweet up front, too. Nice handling. Easy to fly. Outstanding performance (power, slow approach speed, excellent brakes).

Let's not forget that it had teething problems. 2 years late for delivery. Battery fire issues. Not perfect. The "A" model of anything never is, but it looks like Boeing has worked out the bugs in this one and customers (airlines) and their customers (passengers) are very happy with it.

 

[CourierDriver]

Just a thought, go back in time,,,how did the WW2 pilots ever manage to get a B17 from England to Germany and back without all that fancy fly by a computer box....amazing.....

 

[edyvw]

Originally Posted by Astro14
Not anytime soon.

I'm very happy on the 757/767, which is the dinosaur of our fleet, but a good airplane, with excellent power, solid handling, and a great safety record. As an example, I landed in Eagle, CO a while back, with 31,000 lbs of gas, at 6,500 feet elevation, and had no problem turning off the runway early. Such a great airplane!

The 787 is likely the future of aircraft systems architecture. The carbon fuselage, the on-demand systems, etc. have all delivered an airplane that has huge fuel efficiency and range improvements over existing/conventional airplanes.


I flew on Saturday late night, 11/31 from LAS to DEN on 757 and got reminded what a great airplane it is. Lately everything is mostly 320/737 on domestic routes. But I always liked that family of planes.
But yes, new materials, engines etc. will doom 757/767. It will become too expensive per passenger compared to other, newer planes.
I once purposely choose route Toronto-Zurich instead of shorter through ORD or EWR, when 787 started to get out, just after all that battery thing. Air Canada, 787-8. It was nice ride. Quite, no drama, more light etc. It was pleasant ride.

 

[Astro14]

Originally Posted by CourierDriver
Just a thought, go back in time,,,how did the WW2 pilots ever manage to get a B17 from England to Germany and back without all that fancy fly by a computer box....amazing.....


Well, they managed to lose 5% of those bombers each time they did it...not all due to enemy action. Many were lost due to mechanical failure, weather, poor navigation. Lots and lots of crashes.

You OK with that kind of reliability today?

Catch-22? 22 missions and you've beat the odds on being alive?

With 60,000 flights in the US every day, WW II B-17 mission success rates would yield roughly 3,000 airline crashes PER DAY. With over a quarter of a million dead.

Every day.

1000 times the crashes and casualties of 9-11.

Every day.

Nah, the good old days weren't really all that good in aviation...

 

[john_pifer]

Originally Posted by Astro14
Originally Posted by john_pifer
Originally Posted by Kestas
Speaking of maintenance short cuts, that is what took down the DC-10 at O'Hare airport. An engine fell off the plane during takeoff because of short cuts the mechanics took to install the engine.


Also design blunders by McDonnell-Douglas. If the DC-10 had incorporated hydraulic fuses, the crash wouldn't have happened.


Different crashes.

The American DC-10 that crashed in Chicago was the result of fractured engine mount bolts. The engine was hung with a forklift (maintenance malpractice), and that damaged the mounting bolts, which failed during takeoff, resulting in the loss of an engine, hydraulic failure, and airframe damage, including loss of slats, from the engine impacting the wing.

The crew had no chance.

The United DC-10 (United 232) had a no.2 (tail) engine failure that damaged the tail and took out a hydraulic junction, resulting in the loss of all hydraulics, all flight controls.

The crew had no chance.

And yet, in one of the finest moments in aviation, Al Haynes, the Captain, aided by several, including Denny Fitch, another United Captain, managed to fly it to Sioux City, Iowa put it down on the runway there.


https://en.wikipedia.org/wiki/American_Airlines_Flight_191

https://en.wikipedia.org/wiki/United_Airlines_Flight_232

I've never heard of "hydraulic fuses" - and while they sound good, they wouldn't have helped the American DC-10, which lost slat control, or the United DC-10, which had the hydraulics fail in the rudder. If you were to "fuse" a hydraulic system, to close off parts of it, the rudder would be among the top priority parts of the hydraulic system, and would continue to receive fluid...and bleed out anyway...


I was actually referring to the fact that the slats on the DC-10 are hydraulically-actuated, and don't have a mechanism to lock them in the extended position in the event of the loss of hydraulic pressure to the actuators. So, although maintenance negligence was the direct cause of the crash, there's a good chance that the pilots could have saved it if the slats outboard of the engine that separated hadn't retracted.

I remember reading that the other two widebody airliners that came into service around the same time as the DC-10 (L1011, 747) were designed with that feature.

 

[Exhaustgases]

The biggest cause of crashes in the old days was, lack of air traffic control for proper separation. Landings didn't seem to fare well back in the days.
Lack of ground warning systems.

 

[Astro14]

Ah - John, now I see what you're saying.

Yes, if the slats had remained in position on the American flight, then they would've had aircraft control, and it would've been a much different outcome.

After five years of teaching and flying the 747-400, I hadn't heard of hydraulic fuses, though I've Googled it since reading your post...

Locking an actuator in place to enable graceful degradation of performance in the case of a hydraulic failure makes sense.

The F-14 inlet ramps would lock if the respective hydraulic system failed. The hope was that you could get the airplane under control, and slowed down, before a ramp moved and caused the engine to stall/quit.

 

[john_pifer]

Originally Posted by Astro14
Ah - John, now I see what you're saying.

Yes, if the slats had remained in position on the American flight, then they would've had aircraft control, and it would've been a much different outcome.

After five years of teaching and flying the 747-400, I hadn't heard of hydraulic fuses, though I've Googled it since reading your post...

Locking an actuator in place to enable graceful degradation of performance in the case of a hydraulic failure makes sense.

The F-14 inlet ramps would lock if the respective hydraulic system failed. The hope was that you could get the airplane under control, and slowed down, before a ramp moved and caused the engine to stall/quit.


Haven't looked into the specific mechanism that the 747 (or L1011) use for preventing slat retraction if hydraulic pressure to the actuators is lost. It may or may not be a hydraulic fuse setup.

 

[Astro14]

Most of those flap and slat actuators are a jack screw set up, and they won't move if hydraulic pressure is lost. So, no real need for a mechanism to maintain residual pressure and/or fluid in the circuit.

 

[john_pifer]

Originally Posted by Astro14
Most of those flap and slat actuators are a jack screw set up, and they won't move if hydraulic pressure is lost. So, no real need for a mechanism to maintain residual pressure and/or fluid in the circuit.


Yeah, I've never worked on any big jets; I started on regionals when I got out of A&P school, and I've been with Embraer's heavy check facility here for the last few years. The flaps and slats on the ERJ are electrically-actuated, with central motors for each turning torque tubes, which turn jack screws at the actuators.