#214742 - 14/05/2004 14:00
Re: I flew a helicopter today!
[Re: tfabris]
|
journeyman
Registered: 30/12/2001
Posts: 83
|
Ahhh, the 'ole "coputers are safer" argument...here's a short story from my corporate flying days...
On an ILS into Sacramento with my brother as co-pilot, I decided to let the autopilot fly the approach since the weather had gone below minimums AFTER we reached the outer marker. About 1/4 mile out the autopilot found itself a bit high and dove to find the glide slope. All I remember was the radar altimeter light and bell going off and punching the throttles and the autopilot shut-off (overboosting the turbines in the process) for an emergency missed approach. All you could see out all the windows was the fog flashing as we passed over the approach lighting system. As it turns out, I pulled things out at 50 feet above the gound. Significantly lower than the 200 foot minimum at the missed approach point.
In other words, had I let the "computer fly it", both my brother and myself would be dead.
And then there's this (Real Player required)...when the computer went into autoland mode and wouldn't let the pilot override...
Fly-by-wire is fine, but you DAMN well better have a hard-wired safety override. A good pilot's "feel" and knowledge of a plane is often WAY better than an engineers.
|
|
Top
|
|
|
|
|
#214743 - 14/05/2004 14:07
Re: I flew a helicopter today!
[Re: CommOri]
|
carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
|
Your pilot-speak confuses me. Are you saying that the computer almost plowed you into the ground before the runway even started?
_________________________
Bitt Faulk
|
|
Top
|
|
|
|
|
#214744 - 14/05/2004 14:22
Re: I flew a helicopter today!
[Re: wfaulk]
|
carpal tunnel
Registered: 20/12/1999
Posts: 31597
Loc: Seattle, WA
|
Correct, that is exactly what he's saying.
|
|
Top
|
|
|
|
|
#214745 - 14/05/2004 14:38
Re: I flew a helicopter today!
[Re: wfaulk]
|
journeyman
Registered: 30/12/2001
Posts: 83
|
Yeah, that's the gist of it. It would have put us into the ground about 50 yards short of the runway because it was "chasing" the glide slope.
The glide slope is a radio beam shot from the appraoch end of the runway into the air at about 3 degrees. It, combined with the "localizer" (the same thing but aligned horizontally) gives you the ILS path (ILS=Instrument Landing System). It's basically the road you follow through the muck to the runway.
As you get closer to the runway the sensitivity of the ILS becomes greater, so smaller control inputs are needed as correction. For some reason, the autopilot overcontrolled to get back onto the glideslope. We had the plane put into maintenance because of the problem and the shop reported that they could find nothing wrong with the system.
I don't think I ever let the autopilot in that particular plane fly an ILS again (at least not in IFR).
|
|
Top
|
|
|
|
|
#214746 - 14/05/2004 14:52
Re: I flew a helicopter today!
[Re: wfaulk]
|
old hand
Registered: 01/05/2003
Posts: 768
Loc: Ada, Oklahoma
|
Maybe we should have waited until after Amersfoort to tell Bitt this story... 
_________________________
-Michael West
|
|
Top
|
|
|
|
|
#214747 - 14/05/2004 15:05
Re: I flew a helicopter today!
[Re: mwest]
|
carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
|
No. I'm always pretty confident that this is the usual state of affairs. It's the coming to grips with it that's the hard part.
_________________________
Bitt Faulk
|
|
Top
|
|
|
|
|
#214748 - 14/05/2004 16:09
Re: I flew a helicopter today!
[Re: CommOri]
|
pooh-bah
Registered: 13/09/1999
Posts: 2401
Loc: Croatia
|
Ahhh, the 'ole "coputers are safer" argument... Yeah, and pilots are supernatural, infallible beigns... You do read NTSB's preliminary investigation report digests, don't you? Not many navigation equipment breakdowns, plenty of pilot judgment errors. In other words, had I let the "computer fly it", both my brother and myself would be dead. OTOH, had those Ukrainian pilots over German/Swiss border listened to their TCAS and not the human controller, 70-something childern would be alive...  Fly-by-wire is fine, but you DAMN well better have a hard-wired safety override. A good pilot's "feel" and knowledge of a plane is often WAY better than an engineers. I follow this kind of discussion in AW&ST and Flying for ages. Pilots on your side of the fence would say 'So what if I overstress the plane a bit in dangerous situation? Better wrinkled wing skin than hole in the ground.' Yes, but why are they so sure they would 'just wrinkle the wing', not break it, or enter accelerated stall, or stay too far from the limit and fail to use all of the plane capability?
Engineers don't feel the airplane, they model it (then measure its actual performance, then refine their models...). Enourmous amount of feedback from development, testing and early customer pilots is taken (mostly regarding engonomy, consistency of symbology etc). The result is something like A320 where, for example, a pilot deciding a go around is called for just yanks the joystick fully backward: the plane applies TOGA power, raises the gear, retracts the flaps and tries to achieve the best angle of climb airspeed pulling up at the edge of stall (or something like that). A friend who transitioned from ancient B-737-200 to A320 tells me he would not change back for anything.
It is in principle possible to make software as close to bug-free as one wants; it is just a matter of time and resources, that is, money. OTOH, it is impossible to eliminate human error beyond some level quite far from perfect.
_________________________
Dragi "Bonzi" Raos
Q#5196
MkII #080000376, 18GB green
MkIIa #040103247, 60GB blue
|
|
Top
|
|
|
|
|
#214749 - 14/05/2004 16:16
Re: I flew a helicopter today!
[Re: bonzi]
|
carpal tunnel
Registered: 20/12/1999
Posts: 31597
Loc: Seattle, WA
|
It is in principle possible to make software as close to bug-free as one wants; it is just a matter of time and resources, that is, money. OTOH, it is impossible to eliminate human error beyond some level quite far from perfect. Funny. I would have made the exact opposite argument. It's possible to train and educate a human being to be very safe and to use good judgement, but impossible to find every possible bug in a piece of complex code, and impossible to code something so that it can deal with all possible contingencies.
I don't think any rational person argues for "all computer control" or "all human control". Everyone agrees that we still need people in the cockpits because electronic systems, while good and useful, can't do everything. I don't think anyone in their right mind is arguing for electronic systems that can't be overidden.
|
|
Top
|
|
|
|
|
#214750 - 14/05/2004 16:33
Re: I flew a helicopter today!
[Re: tfabris]
|
journeyman
Registered: 30/12/2001
Posts: 83
|
I appreciate the arguments on both sides, but as (1) an ex-professional pilot and (2) a current software engineer, let me say this...
I would much prefer to fly a plane with my hands (or the hands of another competent pilot) than fly a plane by wire that I (or other programmers) programmed.
Also, in reference to my story above, if I hadn't been able to overboost the turbines I may not be here today. A computer likely wouldn't have let me do that. Yes, assuming there was a special-caase programmed in, then yes it would have, but a "keep it within the envelope" system wouldn't have.
Fly-by-wire systems are great for reducing pilot work load (and joysticks are just plain cool), but when the sh*t hits the proverbial fan, I want to control the plane.
Just food for thought. Of course, all of this ignores aircraft that NEED fly by wire systems, like the experimental dynamically unstable designs of new fighters. No to mention, different pilots will have different preferences (hence the never-ending discussion).
|
|
Top
|
|
|
|
|
#214751 - 14/05/2004 16:45
Re: I flew a helicopter today!
[Re: tfabris]
|
pooh-bah
Registered: 13/09/1999
Posts: 2401
Loc: Croatia
|
Funny. I would have made the exact opposite argument. It's possible to train and educate a human being to be very safe and to use good judgement, but impossible to find every possible bug in a piece of complex code, and impossible to code something so that it can deal with all possible contingencies. Again, read those NTSB reports, and see about 15000+ hour pilots doing the most 'stupid' (and fatal) mistakes. As for code, it can be made arbitrarily close to bug-free; it's just that it is too expensive to do for 'ordinary' stuff you and I enconter. I don't think any rational person argues for "all computer control" or "all human control". Everyone agrees that we still need people in the cockpits because electronic systems, while good and useful, can't do everything. I don't think anyone in their right mind is arguing for electronic systems that can't be overidden. This sounds as a religious statement, Tony! You have been exposed (as was I) to too much expensive but lousy code. Many people in aerospace industry believe that completely automated airplanes would be safer than piloted ones (not perfectly safe, of course, just safer than human-operated). Chances are we will soon be able to find out, with UAVs and UCAVs operating in 'regular' airspace. BTW, while it is possible to overide automated navigation equipment, all Airbuses from A320 on, all fourth and fifth generation fighters, all stealth planes and drones and to some extent B-777 are completely fly-by-wire when operation of control surfaces is concerned. There are no direct mechanical or hydraulic links (again, with partial exception of 777).
_________________________
Dragi "Bonzi" Raos
Q#5196
MkII #080000376, 18GB green
MkIIa #040103247, 60GB blue
|
|
Top
|
|
|
|
|
#214752 - 14/05/2004 16:47
Re: I flew a helicopter today!
[Re: CommOri]
|
carpal tunnel
Registered: 29/08/2000
Posts: 14493
Loc: Canada
|
There's a huge difference between a defective autopilot system and some basic level-flight assistance under human control.
In a heliocopter, the pilot is doing everything except pedalling to turn the rotors around -- there's a motor for that job. There should really also be some motors under feedback control to do other jobs, like keeping the machine level and in one place when the pilot wants that to happen. This is quite a bit different from having the pilot just lean back and let a computer fly the whole deal.
-ml
|
|
Top
|
|
|
|
|
#214753 - 14/05/2004 16:57
Re: I flew a helicopter today!
[Re: bonzi]
|
journeyman
Registered: 30/12/2001
Posts: 83
|
Yeah, my dad just retired from United and flew 737, 767/77 and ended up with the 747-400 (among others). I don't think most traditionally trained pilots are too concerned about fly-by-wire (maybe I'm wrong), but my software experience certainly taints things for me.
My thoughts tend to drift into wondering how close to the edge of the envelope will the computer let me go? The answer is obviously a moving target as technologies and, indeed, testing environments and modeling systems change.
Also, even in the traditional "all hardware" flying model my life is hanging by some engineers' idea what is an acceptable failure rate anyway. To quote JP, "Oh God, our lives are in the hands of engineers". As we saw in Sioux City, even redundant hardware systems fail.
It's always an interesting discussion. I just hate adding potential software failure points to a systems that already has enough points of failure in the hardware. Even though I know that we're trading in some hardware failures for software (i.e., no long wires/pulleys or hydraulic lines/valves to fail).
|
|
Top
|
|
|
|
|
#214754 - 14/05/2004 17:11
Re: I flew a helicopter today!
[Re: CommOri]
|
pooh-bah
Registered: 13/09/1999
Posts: 2401
Loc: Croatia
|
Yeah, my dad just retired from United and flew 737, 767/77 and ended up with the 747-400 (among others). I don't think most traditionally trained pilots are too concerned about fly-by-wire (maybe I'm wrong), but my software experience certainly taints things for me. Well, I was concerned, too, when I read that Avidyne's MFD OS was WinNT-based  My thoughts tend to drift into wondering how close to the edge of the envelope will the computer let me go? The answer is obviously a moving target as technologies and, indeed, testing environments and modeling systems change. Agreed Also, even in the traditional "all hardware" flying model my life is hanging by some engineers' idea what is an acceptable failure rate anyway. To quote JP, "Oh God, our lives are in the hands of engineers". As we saw in Sioux City, even redundant hardware systems fail. True, who knows how many screws, hoses and flanges are non-redundant points of failure in your average light plane? Actually, it amazes me how often trivial mechanical components feature in those accident reports (right behind judgment errors or just plain lack of skill in low-time amateur pilots). It's always an interesting discussion. I just hate adding potential software failure points to a systems that already has enough points of failure in the hardware. Even though I know that we're trading in some hardware failures for software (i.e., no long wires/pulleys or hydraulic lines/valves to fail). Again, agreed: in principle, simpler system should be inherently more reliable. But, let me repeat: the human component is often the weakest link... 
_________________________
Dragi "Bonzi" Raos
Q#5196
MkII #080000376, 18GB green
MkIIa #040103247, 60GB blue
|
|
Top
|
|
|
|
|
#214755 - 14/05/2004 17:45
Re: I flew a helicopter today!
[Re: bonzi]
|
carpal tunnel
Registered: 25/12/2000
Posts: 16706
Loc: Raleigh, NC US
|
Dare I point out that humans also create the software?
_________________________
Bitt Faulk
|
|
Top
|
|
|
|
|
#214757 - 15/05/2004 10:26
Re: I flew a helicopter today!
[Re: wfaulk]
|
pooh-bah
Registered: 13/09/1999
Posts: 2401
Loc: Croatia
|
Dare I point out that humans also create the software? Heh, Bitt, I expected this
People are not very good at split-second decisions, keeping focused on boring task for long time, judgment free of preconceptions, pressures etc; our sense of orientation, acceleration and turn rate in 3D is easily fooled; when judging speed and distance we automaticaly use cues that might or might not be appropriate... In all this, essential for safe operation of aircraft, machines can be made to perform better (since the problem space is relatively small, predictable and easily defined).
Of course, being written by humans, aircraft control and/or navigation software will contain errors. My point was that, given enough time and resources, software (possibly in complex setup like multiple-redundant 'voting' systems with different, independently designed and implemented hardware and software) can be made arbitrarily close to error-free. I think we are near (or perhaps even past) the point where cost of such a system (plus the cost of residual errors) is lower than the cost we are willing to pay for human errors. This cost of human-replacing control systems is, of course, non-trivial: couple of hundred thousand bucks will not cut it...
_________________________
Dragi "Bonzi" Raos
Q#5196
MkII #080000376, 18GB green
MkIIa #040103247, 60GB blue
|
|
Top
|
|
|
|
|
#214758 - 15/05/2004 10:34
Re: I flew a helicopter today!
[Re: mlord]
|
pooh-bah
Registered: 09/08/2000
Posts: 2091
Loc: Edinburgh, Scotland
|
This technology already exists and is used - my kid brother used to fly Sea Kings on search and rescue and anti-terrorism missions. When hovering with a sonar buoy dropped, they push a button and they hover at fixed height and position. Admittedly he did say it was utterly boring and he has since moved to Gazelles - apparently like going from driving a bus to a formula 1 race car.
Oh, and there are a couple of helicopters which will fly inverted. The most famous is the Lynx. The critical issue is that most choppers have blades which flex - they bend up when lift is applied. Normally this is fine, but when inverted this bend means the blades will chop off the tail! Barrel rolls are fine as the centripetal force means your feet always feel 'down' but you need rigid blades to do 'real' inverted flight. And it isn't recommended even in a Lynx, as this brings it very close to limits.
_________________________
Rory
MkIIa, blue lit buttons, memory upgrade, 1Tb in Subaru Forester STi
MkII, 240Gb in Mark Lord dock
MkII, 80Gb SSD in dock
|
|
Top
|
|
|
|
|
#214759 - 15/05/2004 10:44
Re: I flew a helicopter today!
[Re: CommOri]
|
pooh-bah
Registered: 13/09/1999
Posts: 2401
Loc: Croatia
|
...when the computer went into autoland mode and wouldn't let the pilot override... Ah, I didn't follow the link because I don't have Real, but have just read Roger's post. This "computer wouldn't let pilot..." is urban myth (conspiracy theorist would say perpetuated by Boeing ). I remember that investigation has shown exactly the opposite: the plane's control system was switched to "direct contol laws" (closest to "manual" there is in A320) and pilots misjudged the altitude (ignoring assorted horns, beeps, "terrain, tarrain!"s and "pull up, pull up"s). Flight deck conversation indicated the morons intended to do a very low altitude fly-by (I don't remember who was to be impressed by it).
So, as a rough translation of a Croatian saying would put it, this "diverts water to my mill".
_________________________
Dragi "Bonzi" Raos
Q#5196
MkII #080000376, 18GB green
MkIIa #040103247, 60GB blue
|
|
Top
|
|
|
|
#214760 - 15/05/2004 10:52
Re: I flew a helicopter today!
[Re: frog51]
|
pooh-bah
Registered: 13/09/1999
Posts: 2401
Loc: Croatia
|
And it isn't recommended even in a Lynx, as this brings it very close to limits. Frankly, it is hard to imagine why it would be recommended, but it certainly is cool.
_________________________
Dragi "Bonzi" Raos
Q#5196
MkII #080000376, 18GB green
MkIIa #040103247, 60GB blue
|
|
Top
|
|
|
|
|
|
Previous Topic
Index