reverse before touch down
I second the, Ummm... what????
Where is that written in ANY Boeing, Airbus, Embraer FCTM or OM????
A disproportionate number of pod scrapes were caused by the stupidity of crew placing their hands on the TR levers and lifting one immediately on touchdown, where a bounce or skip resulted. Make no mistake, if I am a passenger in an aircraft and see a TR deploy on any Jet airborne, the regulator will get all the information that I can put together. As a training point, IN THE SIMULATOR, if someone puts their hands on the TR's in the flare, I called GA. If they did it in an aircraft while I was doing standards, they got another evaluation ride. If you do it on any of my jets, I will get your hands off the levers. It is unconscionable to risk the aircraft just because the pilot doesn't know where to put his damned hands. If you need to recklessly endanger yourself by landing on a runway that is so short that you are compelled to do a non standard procedure, then you have already made a bad decision. No OEM recommends immediate TR on touchdown, before the aircraft is fully ground bound. Forgetting the spoilers will get you into serious problems in this event.
WTF!
Back in the military we used to pull reverse in the air, work fine if it is symmetrical and everything else works correctly. Any error and people die. People did die doing that.
FYI, the cause was slightly different, but this is the sort of outcome that lies in wait of having one engine in full thrust (for a dart that is a relative term) and one that is not, at low speed. If you think it is fine to grab early reverse, just tell the passengers what your VMCair or VMCground is for having one engine in reverse (even at idle) and the other at GA thrust.
Where is that written in ANY Boeing, Airbus, Embraer FCTM or OM????
A disproportionate number of pod scrapes were caused by the stupidity of crew placing their hands on the TR levers and lifting one immediately on touchdown, where a bounce or skip resulted. Make no mistake, if I am a passenger in an aircraft and see a TR deploy on any Jet airborne, the regulator will get all the information that I can put together. As a training point, IN THE SIMULATOR, if someone puts their hands on the TR's in the flare, I called GA. If they did it in an aircraft while I was doing standards, they got another evaluation ride. If you do it on any of my jets, I will get your hands off the levers. It is unconscionable to risk the aircraft just because the pilot doesn't know where to put his damned hands. If you need to recklessly endanger yourself by landing on a runway that is so short that you are compelled to do a non standard procedure, then you have already made a bad decision. No OEM recommends immediate TR on touchdown, before the aircraft is fully ground bound. Forgetting the spoilers will get you into serious problems in this event.
WTF!
Back in the military we used to pull reverse in the air, work fine if it is symmetrical and everything else works correctly. Any error and people die. People did die doing that.
FYI, the cause was slightly different, but this is the sort of outcome that lies in wait of having one engine in full thrust (for a dart that is a relative term) and one that is not, at low speed. If you think it is fine to grab early reverse, just tell the passengers what your VMCair or VMCground is for having one engine in reverse (even at idle) and the other at GA thrust.
Last edited by fdr; 2nd Mar 2019 at 06:19.
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DC8-60 Series: inboard reversers available in flight with gear handle in up position, but restricted to reverse power stop. All 4 engines with gear handle in down position. I think the older series where similar.
Trident: reversers on engines 1 & 3 available in flight – the descent rate was in rather interesting to say the least. Reverse thrust was indeed selected just before touch down (below 50 ft RA).
MP
Trident: reversers on engines 1 & 3 available in flight – the descent rate was in rather interesting to say the least. Reverse thrust was indeed selected just before touch down (below 50 ft RA).
MP
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I second the, Ummm... what????
Where is that written in ANY Boeing, Airbus, Embraer FCTM or OM????
A disproportionate number of pod scrapes were caused by the stupidity of crew placing their hands on the TR levers and lifting one immediately on touchdown, where a bounce or skip resulted. Make no mistake, if I am a passenger in an aircraft and see a TR deploy on any Jet airborne, the regulator will get all the information that I can put together. As a training point, IN THE SIMULATOR, if someone puts their hands on the TR's in the flare, I called GA. If they did it in an aircraft while I was doing standards, they got another evaluation ride. If you do it on any of my jets, I will get your hands off the levers. It is unconscionable to risk the aircraft just because the pilot doesn't know where to put his damned hands. If you need to recklessly endanger yourself by landing on a runway that is so short that you are compelled to do a non standard procedure, then you have already made a bad decision. No OEM recommends immediate TR on touchdown, before the aircraft is fully ground bound. Forgetting the spoilers will get you into serious problems in this event.
WTF!
Back in the military we used to pull reverse in the air, work fine if it is symmetrical and everything else works correctly. Any error and people die. People did die doing that.
FYI, the cause was slightly different, but this is the sort of outcome that lies in wait of having one engine in full thrust (for a dart that is a relative term) and one that is not, at low speed. If you think it is fine to grab early reverse, just tell the passengers what your VMCair or VMCground is for having one engine in reverse (even at idle) and the other at GA thrust.
Where is that written in ANY Boeing, Airbus, Embraer FCTM or OM????
A disproportionate number of pod scrapes were caused by the stupidity of crew placing their hands on the TR levers and lifting one immediately on touchdown, where a bounce or skip resulted. Make no mistake, if I am a passenger in an aircraft and see a TR deploy on any Jet airborne, the regulator will get all the information that I can put together. As a training point, IN THE SIMULATOR, if someone puts their hands on the TR's in the flare, I called GA. If they did it in an aircraft while I was doing standards, they got another evaluation ride. If you do it on any of my jets, I will get your hands off the levers. It is unconscionable to risk the aircraft just because the pilot doesn't know where to put his damned hands. If you need to recklessly endanger yourself by landing on a runway that is so short that you are compelled to do a non standard procedure, then you have already made a bad decision. No OEM recommends immediate TR on touchdown, before the aircraft is fully ground bound. Forgetting the spoilers will get you into serious problems in this event.
WTF!
Back in the military we used to pull reverse in the air, work fine if it is symmetrical and everything else works correctly. Any error and people die. People did die doing that.
FYI, the cause was slightly different, but this is the sort of outcome that lies in wait of having one engine in full thrust (for a dart that is a relative term) and one that is not, at low speed. If you think it is fine to grab early reverse, just tell the passengers what your VMCair or VMCground is for having one engine in reverse (even at idle) and the other at GA thrust.
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Yes, I can name a few. All pilots of classic aircraft such as the 707/A300/747 combis..
Airbus A320 family have a useful partial ground spoiler mode where if one main landing gear has weight on wheels, selecting idle reverse will give you 10 deg spoiler deployment to reduce wing lift and ease the aircraft down. (As long as the spoilers were armed before landing, which is SOP anyway).
Last edited by Uplinker; 6th Mar 2019 at 08:55.
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Does part 25/cs25 prohibit in flight reverse? Or is it not more of, it’s not a requirement of civilian jets to drop 20k/min and therefore an unnecessary feature?
Now, look at what happened on Lauda - the reverser deployed on one side (uncommanded) - the resultant upset caused complete loss of control in a few seconds and aircraft breakup shortly there after. In order to certify in-flight reverse use, you'd have to definitively show that Lauda couldn't happen if you got unsymmetrical reverse deployment.
I very seriously doubt you could get there (and I sure as hell wouldn't want to be on a flight test to try it).
Beside, yes, it's an unnecessary feature. Passenger O2 requirements assume an idle descent from the max certified altitude - no need to get down even quicker than that. And in the extraordinary event that you do need to come down faster than idle with speed brakes, you're best bet is to drop the landing gear - it may cause damage to the gear doors, but it's readily controllable.
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No, in-flight reverse is not specifically prohibited. However, everything needs to comply with 25.1309 - which in short means that the probability of a catastrophic event has to be less than 1 in a billion (per flight hour) and that no single failure can have a catastrophic outcome (i.e. you can't use probability arguments for single failures, structural elements excluded).
Now, look at what happened on Lauda - the reverser deployed on one side (uncommanded) - the resultant upset caused complete loss of control in a few seconds and aircraft breakup shortly there after. In order to certify in-flight reverse use, you'd have to definitively show that Lauda couldn't happen if you got unsymmetrical reverse deployment.
I very seriously doubt you could get there (and I sure as hell wouldn't want to be on a flight test to try it).
Beside, yes, it's an unnecessary feature. Passenger O2 requirements assume an idle descent from the max certified altitude - no need to get down even quicker than that. And in the extraordinary event that you do need to come down faster than idle with speed brakes, you're best bet is to drop the landing gear - it may cause damage to the gear doors, but it's readily controllable.
Now, look at what happened on Lauda - the reverser deployed on one side (uncommanded) - the resultant upset caused complete loss of control in a few seconds and aircraft breakup shortly there after. In order to certify in-flight reverse use, you'd have to definitively show that Lauda couldn't happen if you got unsymmetrical reverse deployment.
I very seriously doubt you could get there (and I sure as hell wouldn't want to be on a flight test to try it).
Beside, yes, it's an unnecessary feature. Passenger O2 requirements assume an idle descent from the max certified altitude - no need to get down even quicker than that. And in the extraordinary event that you do need to come down faster than idle with speed brakes, you're best bet is to drop the landing gear - it may cause damage to the gear doors, but it's readily controllable.
So on the C17, im fairly sure a similar probability loss model is used. If 2 of 3 interlock prox sensors indicate TR deployment in flight (or if 2 prox sensors fail in flight and loose resilience), the controller automatically commands flight idle on that engine. So its not impossible (nor difficult) to meet FAR/CS25 requirements in a modern aircraft design if this design were adopted. But again, structure would need to be beefed up (weight cost, complexity etc), and there is no role requirement for it, hence why its not a design feature.
If I were in a similar scenario in a commercial equivalent (Lauda scenario) the T-Handle would be the best place to start I suspect. But that would require very rapid actions and realization of what is happening pretty quickly.
Last edited by VinRouge; 7th Mar 2019 at 13:43.
Precisely. There was a case in KATL where an Eastern DC9 was dispatched with a thrust reverser inop which required MTC to perform some actions back near the engine to isolate the reverse mechanism from hydraulics (the details of that escape me at the moment). This had to have been in the late 1970s, early 1980s.
Well, the MTC action wasn't done correctly and the inop reverser came open at rotation on takeoff. The crew overcame the surprise and got the airplane into the air and back on the ground. It was a real feat of airmanship.
We tried it in the sim and found the only way to not lose control of the airplane was to snap the throttle to idle and shut off the fuel. It was still a handful even when we knew it was coming.
Those EAL guys really did a great job. I tried to find an article about it but couldn't.
i
Last edited by bafanguy; 7th Mar 2019 at 20:25.
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VinRouge,
Precisely. There was a case in KATL where an Eastern DC9 was dispatched with a thrust reverser inop which required MTC to perform some actions back near the engine to isolate the reverse mechanism from hydraulics (the details of that escape me at the moment). This had to have been in the late 1970s, early 1980s.
Well, the MTC action wasn't done correctly and the inop reverser came open at rotation on takeoff. The crew overcame the surprise and got the airplane into the air and back on the ground. It was a real feat of airmanship.
We tried it in the sim and found the only way to not lose control of the airplane was to snap the throttle to idle and shut off the fuel. It was still a handful even when we knew it was coming.
Those EAL guys really did a great job. I tried to find an article about it but couldn't.
i
Precisely. There was a case in KATL where an Eastern DC9 was dispatched with a thrust reverser inop which required MTC to perform some actions back near the engine to isolate the reverse mechanism from hydraulics (the details of that escape me at the moment). This had to have been in the late 1970s, early 1980s.
Well, the MTC action wasn't done correctly and the inop reverser came open at rotation on takeoff. The crew overcame the surprise and got the airplane into the air and back on the ground. It was a real feat of airmanship.
We tried it in the sim and found the only way to not lose control of the airplane was to snap the throttle to idle and shut off the fuel. It was still a handful even when we knew it was coming.
Those EAL guys really did a great job. I tried to find an article about it but couldn't.
i
So on the C17, im fairly sure a similar probability loss model is used. If 2 of 3 interlock prox sensors indicate TR deployment in flight (or if 2 prox sensors fail in flight and loose resilience), the controller automatically commands flight idle on that engine. So its not impossible (nor difficult) to meet FAR/CS25 requirements in a modern aircraft design if this design were adopted. But again, structure would need to be beefed up (weight cost, complexity etc), and there is no role requirement for it, hence why its not a design feature.
If I were in a similar scenario in a commercial equivalent (Lauda scenario) the T-Handle would be the best place to start I suspect. But that would require very rapid actions and realization of what is happening pretty quickly.
If I were in a similar scenario in a commercial equivalent (Lauda scenario) the T-Handle would be the best place to start I suspect. But that would require very rapid actions and realization of what is happening pretty quickly.
ed. Simply failing to wait until the engine spooled down to idle before commanding in-flight reverse could be catastrophic with asymmetric reverse at altitude.With the old pure jet and low bypass engines, in-flight reverse - even if something went wrong - wasn't a big deal. But what we didn't know before Lauda was that with high bypass engines it's a whole different story (and the F117 - aka PW2000 - is most definitely a high bypass engine). Had the C-17 been Part 25 certified, in-flight reverse would have been banned in the aftermath of Lauda.
The Lauda crew knew that something funny was going on with the reverser before the deployment occurred - but still were unable to perform a shutdown of the engine in time to prevent complete loss of control. and the resultant aircraft breakup.
Boeing looked at doing a Part 25 cert of the C-17 (abandoned due to insufficient interest to justify the costs). In flight reverse would have been among the first things to get deleted.
Edited to add - the C-17 was designed and put into production pre-Lauda. They hadn't yet learned the Lauda lesson of what high bypass reverse in-flight can do. The analysis that the 767/PW4000 reverser was safe - even with an in-flight deployment - was done as part of the certification. Problem was it was WRONG.
We know better now.
