rwessel From United States of America, joined Jan 2007, 1991 posts, RR: 2 Reply 3, posted (3 months 5 days 21 hours ago) and read 7264 times:
Quoting travelavnut (Reply 2): That's no reason, the 777 and 787 are FBW as well and still use yokes.
Actually it more-or-less is. Yokes and the like were invented to increase the mechanical advantage for pilots as aircraft got bigger. If you have no manual reversion at all, that need goes away, so in a sense FBW makes it possible to use a stick.
Perhaps the real question is why the FBW 777 and 787 have yokes? (Yes, yes, I know: for commonality.)
Max Q From United States of America, joined May 2001, 3290 posts, RR: 19 Reply 4, posted (3 months 5 days 21 hours ago) and read 7252 times:
Quoting rwessel (Reply 3):
Perhaps the real question is why the FBW 777 and 787 have yokes? (Yes, yes, I know: for commonality.)
It's a lot more than that. Boeing decided, very wisely that interconnected yokes and back driven autothrottles were and are essential cues for complete Pilot awareness of their Aircraft's state at all times.
The best contribution to safety is a competent Pilot.
rwessel From United States of America, joined Jan 2007, 1991 posts, RR: 2 Reply 5, posted (3 months 5 days 21 hours ago) and read 7243 times:
Quoting Max Q (Reply 4): It's a lot more than that. Boeing decided, very wisely that interconnected yokes and back driven autothrottles were and are essential cues for complete Pilot awareness of their Aircraft's state at all times.
You can certainly do back-driven or interconnected sticks, although clearly Airbus did not.
rfields5421 From United States of America, joined Jul 2007, 6150 posts, RR: 25 Reply 7, posted (3 months 5 days 20 hours ago) and read 7199 times:
Quoting Max Q (Reply 6): Not really answering the question why Mcd decided to put joysticks in a transport.
Because McD was not Boeing/ anti-Boeing at the time?
More likely, McD was building a lot of stick military fighter type aircraft/ design - and the stick in a military transport isn't a big design concept change from their existing knowledge base.
A friend of mine who had his PPL in small GA aircraft got accepted to the USAF-Res Pilot program (He was a full time USAF-Res SSGT). He did his T-6 training, his T-1 training and his C-17 training. He said the C-17 is the easiest aircraft he has flown due to the stick. Very intuitive and natural - and it leaves him better access to view the displays and use the control panel buttons than a yoke.
This is someone who was firm yoke man until he started T-6 training.
I'll have to ask if the C-17 sticks and throttles are back driven when he returns from the other side of the world.
oldeuropean From Germany, joined May 2005, 1903 posts, RR: 4 Reply 8, posted (3 months 5 days 18 hours ago) and read 7126 times:
Quoting Max Q (Reply 4): Boeing decided, very wisely that interconnected yokes and back driven autothrottles were and are essential cues for complete Pilot awareness of their Aircraft's state at all times.
Well, perhaps for truck drivers. I've never heart of pilots, using joysticks, reporting about problems with the awarness of their aircraft's state.
Max Q From United States of America, joined May 2001, 3290 posts, RR: 19 Reply 10, posted (3 months 4 days 16 hours ago) and read 6296 times:
Just a little thread drift here.
No one has really been able to explain why Mcd decided on a joystick rather than a yoke in a transport aircraft.
I'm not criticizing the choice but am still curious as to how they came up with this decision.
The best contribution to safety is a competent Pilot.
bikerthai From United States of America, joined Apr 2010, 1598 posts, RR: 4 Reply 13, posted (3 months 4 days 12 hours ago) and read 6170 times:
Quoting rfields5421 (Reply 7): More likely, McD was building a lot of stick military fighter type aircraft/ design - and the stick in a military transport isn't a big design concept change from their existing knowledge base.
This seems most logical. Although at the time how much cross-pollination occurred between the St. Louis folks vs the Long Beach folks?
If you have the design and software already built for fighter and only need tweaking for transport, then why not?
I bet the real reason is probably more mundane . . . how much does a yoke weigh vs a stick (assuming the rest of the fly by wire system remains the same).
Quoting NoUFO (Reply 14):
As if weight would make a difference.
No, not the weight of the aircraft but if you can save 2 lbs going from yokes to sticks without inuring any additional cost, then the decision is easy . . . go with the lighter design. Someone probably got an atta boy for that
NBGSkyGod From United States of America, joined May 2004, 597 posts, RR: 1 Reply 15, posted (3 months 4 days 7 hours ago) and read 5989 times:
I may be talking out of my butt since I can't find the reference, but I seem to remember the USAF wanted a stick since in the beginning of the program much of the source pool of pilots were coming from fighters, and it seemed a more natural transition with the stick rather than a yoke.
"I use multi-billion dollar military satellite systems to find tupperware in the woods."
Bongodog1964 From United Kingdom, joined Oct 2006, 3019 posts, RR: 2 Reply 16, posted (3 months 3 days 8 hours ago) and read 5780 times:
Quoting Max Q (Reply 19): No one has really been able to explain why Mcd decided on a joystick rather than a yoke in a transport aircraft.
I'm not criticizing the choice but am still curious as to how they came up with this decision.
Perhaps they just viewed yokes as no longer necessary (as have Airbus) The question perhaps ought to be why do Boeing persist with this antiquated piece of ironwork when its no longer has any piano wire attached to operate the controls.
Max Q From United States of America, joined May 2001, 3290 posts, RR: 19 Reply 17, posted (3 months 3 days 1 hour ago) and read 5688 times:
Quoting Bongodog1964 (Reply 25):
Perhaps they just viewed yokes as no longer necessary (as have Airbus) The question perhaps ought to be why do Boeing persist with this antiquated piece of ironwork when its no longer has any piano wire attached to operate the controls.
Didn't really want to bet into the Boeing / Airbus thing here or dignify your response but I would say that having an interconnected yoke and back driven autothrottles are a significant asset to mode awareness and a safer arrangement
in general.
I'm sure the C17's sticks are interconnected and that it has moving autothrottles.
The best contribution to safety is a competent Pilot.
moo From Falkland Islands, joined May 2007, 3596 posts, RR: 4 Reply 19, posted (3 months 2 days 17 hours ago) and read 5570 times:
Quoting Max Q (Reply 26): back driven autothrottles are a significant asset to mode awareness and a safer arrangement
in general.
Back driven autothrottles actually contributed to the Kegworth air crash in 1989, because the throttle levers were linked in the Boeing 737-400 and did not operate independently - the autothrottle adjusted the fuel flow asymmetrically in response to one of hte engines losing thrust, but did not alter the throttle positions as this would adversely affect the other engines fuel flow. Disconnecting the autothrottles to shut down the wrong engine automatically reduced the fuel flow back to the level indicated as required by the position of the throttle - this reduced engine vibration enough to allow the crew to think they had shut down the correct engine.
The crew were led to believe something that was not true, because they thought the throttle position would change - if they did not think this, they would have made other checks to ensure they had infact shut down the correct engine.
Wow, you are so far off base I don't know where to start. First of all on the 737-400 the thrust levers are in no way physically interconnected, they operate independent of each other. Second the autothrottle clutch pack for each engine is located in the E/E bay in the middle of the body cable run. Any input of the auto throttle will cause the the associated thrust lever to move. By a quick review of the accident report, it appears the #1 autothrottle retarded to a reduced target N1 at the same time the autothrottle was disconnected. This allowed the #1 engine to recover from its stall and gave the crew the incorrect impression that by their retarding the #2 engine to idle the situation had improved.
Whether back driven controls are safer or not is not relevant. All governing bodies throughout the world accept either control philosophy, so each has been determined to be acceptably safe.
Max Q From United States of America, joined May 2001, 3290 posts, RR: 19 Reply 21, posted (3 months 2 days 8 hours ago) and read 5348 times:
Quoting yeelep (Reply 29):
Wow, you are so far off base I don't know where to start. First of all on the 737-400 the thrust levers are in no way physically interconnected, they operate independent of each other. Second the autothrottle clutch pack for each engine is located in the E/E bay in the middle of the body cable run. Any input of the auto throttle will cause the the associated thrust lever to move. By a quick review of the accident report, it appears the #1 autothrottle retarded to a reduced target N1 at the same time the autothrottle was disconnected. This allowed the #1 engine to recover from its stall and gave the crew the incorrect impression that by their retarding the #2 engine to idle the situation had improved.
Well said. One of the factors in the Kegworth accident was the layout of the engine instruments which was asymetric and not intuitive.
The best contribution to safety is a competent Pilot.
Perhaps you need to read the accident detail and commentary surrounding the crash in more detail, and the reason for my post becomes obvious.
When in auto throttle mode, there is only one motor to adjust both throttle levers on the 737-400 - if the auto throttle has to adjust only one engines throttle, it cannot move just that one engines throttle lever in indication, it has to make the decision to move both or neither.
In the Kegworth crash, the problem engine (through losing a fan blade) lost power - the auto throttle saw the loss of thrust from the engine and increased thrust demands accordingly but didn't move the thrust lever. The crew expected a change of position of the lever, and as they did not see one they were relying on instrumentation to show which engine failed, and that instrumentation was poor and different to prior variants of the 737.
Wen the crew chose which engine to shut down, they were not aware that one engine had had a throttle increase demand placed on it by the auto throttle.
When they disengaged the auto throttle to shut down the wrong engine, they automatically reduced the damaged engines thrust level to that indicated by the levers position - because it hadn't changed when the auto throttle changed the thrust demands - which had the side effect of reducing the engines vibration issues, leading the crew to believe they had indeed shut down the correct engine.
If they had not been reliant on thrust levers changing positions, and if they had had cause to have to rely on the instruments for that information, it's doubtful that they would have made the assumptions they did.
I never said that the auto throttles caused the crash, nor did I say it was the prime contributor - however, the behaviour of the auto throttles did indeed contribute to the crash as is well documented.
135mech From United States of America, joined Oct 2006, 357 posts, RR: 2 Reply 24, posted (3 months 1 day 14 hours ago) and read 5127 times:
Quoting Max Q (Reply 4): Quoting rwessel (Reply 3):
Perhaps the real question is why the FBW 777 and 787 have yokes? (Yes, yes, I know: for commonality.)
It's a lot more than that. Boeing decided, very wisely that interconnected yokes and back driven autothrottles were and are essential cues for complete Pilot awareness of their Aircraft's state at all times.
In the 5-hour show on how the 777 was built and came to be, they [Boeing] specifically mentioned this... and it is as Max Q states. However, the C-17 was not a part of that as they were created by McDonnell Douglas (later acquired by Boeing) most likely did this as a weight savings option because of it's mission of medium to heavy lift cargo. When making these birds, just like in the commercial world, every ounce/kg/lb counts. And yes, weight of the Yoke isn't just a few pounds, it's actually significant due to the back-driven system needs and added components to put all of the "artificial feel" back into the yokes. I read a long time ago, that was one of the reasons Airbus avoided the yokes altogether (because it was not "needed" with the modern FBW).
135Mech
[Edited 2013-02-21 10:20:49]
25 bikerthai: . Good point. A back driven system with a yoke would be much heavier than the yoke itself. And a back driven system for the yoke would also be much h
26 yeelep: I'm sorry, but this is completely wrong. There are two autothrottle servo mechanisms, one for each engine. They are in no way connected to each other
27 SeaTran: I don't know why the engineers decided to put a stick (not a joystick) in the C-17, but I like it much, much, much better than a yoke. I've flown the
28 Aesma: The A400M has a sidestick like other Airbus fbw planes. I guess it's fine for tactical landings and stuff like that. The Beriev be-200 amphibian jet w
29 bikerthai: Yes, and all the kids growing up in the previous generation grew up with joy sticks. Wonder when they are going to introduce the game controller into
30 dlednicer: To quote from Bill Norton's book "STOL Progenitors: The Technology Path to Large STOL Aircraft and the C-17A": "As the AMST test pilots had requested,
31 Max Q: Best information yet, now it all makes sense. Thanks very much dled.
32 GlobalMoose: So many questions … I’ll try and answer all of them for you! Stay with me, I’ve got a lot of good info for you, try and avoid the TL;DR! It is a
33 Max Q: More great info G Moose, thanks for that. Questions, what is your normal cruise Mach, and Max ? What is the range of the latest C17's
34 GlobalMoose: For your reading pleasure: http://www.boeing.com/defense-space/military/c17/docs/c17_overview.pdf Cruise Mach .74-.77 160,000 lb payload range - 2420
36 sturmovik: May not be as far off as you think. On reason that's accelerated the development of touch screens in the cockpit is because they've become such a hug
37 ThePointblank: Indeed; the first touch screen cockpits have already appeared: This is one from the F-35; it's two 8x10-inch displays, completely multi-touch screen.
38 sturmovik: The difference on the business/general aviation side is that they're taking a slightly different approach. In most cases that I'm aware of, the MCDU
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