The obvious risk being that if the reverse levers don't lock out the main thrust levers (and thus vice versa)

Yeah Mark, I believe that risk should be remote. Just as improbable as breaking the yoke or breaking the gear lever or something. As a kid I also always wondered if there was some sort of electro-mechanic, -magnetic, -hydraulic, -pneumatic or whatever assembly that locks out the fwd versus the reverse thrust levers, but it really is just a mechanical construct, IIRC. Of which I can't exactly find pictures of at the moment, unfortunately. I think the reverse levers have a sort of a horizontal solid metal pin at their bottom base, that travels under a metal track in the forward thrust lever range. Only at the very rear end (at the fwd thrust idle position) there is a little notch, so the pin can go through it, hence allowing upward movement of the rev levers. Then again, this could just be how it was in the sim I remember, really would have to check in the real thing to be sure... :(

To my knowledge there isn't a single aircraft that allows this to occur. The amount of reverse thrust is controlled by how far you pull the reverse levers past reverse idle in every aircraft capable of reverse I know of.Also in response to the first question (how do they work), for the NG specifically, see my post in the MD-11 forum HERE. The engines may be different but the operation principle is identical.

There's plenty! Like some already mentioned earlier in this thread, I can add that it was apperently SOP on the TU154'sFRED

There's plenty! Like some already mentioned earlier in this thread, I can add that it was apperently SOP on the TU154'sFRED

I don't know very much about the TU154 but no other aircraft mentioned in this thread allowed the throttles to be moved forward while the reversers are engaged. Even though with a majority of aircraft only the bypass air is redirected, keep in mind that at low altitude, that's 80% of the thrust coming from the engine. So in the case of the NG assuming 27000 lbs of thrust at full throttle, that means the reverser system would have to withstand over 21000lbs of force trying to rip it off. With that much reverse thrust, the aircraft would just about be able to go over 100kts backwards...assuming the turbine section could handle all the air being forced up the tail pipe.

Etienne, thank you for the clarification. That was exactly as I understood they worked. The obvious risk being that if the reverse levers don't lock out the main thrust levers (and thus vice versa) there would be a very high risk of the reversers being inadvertently deployed when the crew are actually trying to effect a go-around by shoving the levers forward!I'm not familiar with any aircraft that would use such a design. Though if anyone could point one out to me I'd be interested.

Typing is hard on the mobile site with that little iPhone

I don't know very much about the TU154 but no other aircraft mentioned in this thread allowed the throttles to be moved forward while the reversers are engaged. Even though with a majority of aircraft only the bypass air is redirected, keep in mind that at low altitude, that's 80% of the thrust coming from the engine. So in the case of the NG assuming 27000 lbs of thrust at full throttle, that means the reverser system would have to withstand over 21000lbs of force trying to rip it off. With that much reverse thrust, the aircraft would just about be able to go over 100kts backwards...assuming the turbine section could handle all the air being forced up the tail pipe.

Although about 80% of the airflow is reversed, the air is deflected back at an angle to the engines axis, so not all of that would be in the reverse direction, probably 70% or less. There are also losses due to the flow reversal. And you still have the 20% of the thrust from the engine core still acting in the forward direction. So the net reverse thrust is very much less than the figure you mention. Achieving 100 knots in reverse seems quite high to me.So in the case of the NG, reverse thrust (per engine) is approx 70% of 21,000 lbs, i.e. 14,700 per engine. There will still be 6,000 lbs from the core acting in the forward direction, so the net reverse thrust is about 8,700 lbs.Kevin Hall

Although about 80% of the airflow is reversed, the air is deflected back at an angle to the engines axis, so not all of that would be in the reverse direction, probably 70% or less. There are also losses due to the flow reversal. And you still have the 20% of the thrust from the engine core still acting in the forward direction. So the net reverse thrust is very much less than the figure you mention. Achieving 100 knots in reverse seems quite high to me.So in the case of the NG, reverse thrust (per engine) is approx 70% of 21,000 lbs, i.e. 14,700 per engine. There will still be 6,000 lbs from the core acting in the forward direction, so the net reverse thrust is about 8,700 lbs.Kevin Hall

Sorry for the confusion. 21,000lb figure I mentioned was just how much force would be acting on the reverser system, not how much thrust you'd actually get if your could throttle the engines to full in reverse. But even 8,700lbs is a pretty good amount of reverse thrust. Keep in mind that the reversers in general don't provide very much stopping power at all. The spoilers actually do a better job of slowing the aircraft than the reversers. This is why you never see the effects of the reversers factored on landing performance charts.

Sorry for the confusion. 21,000lb figure I mentioned was just how much force would be acting on the reverser system, not how much thrust you'd actually get if your could throttle the engines to full in reverse. But even 8,700lbs is a pretty good amount of reverse thrust. Keep in mind that the reversers in general don't provide very much stopping power at all. The spoilers actually do a better job of slowing the aircraft than the reversers. This is why you never see the effects of the reversers factored on landing performance charts.

Perhaps not enough to reach 100 knots or more though. :( You're right that reverse thrust stopping power is not great compared to spoilers or wheel brakes (on a dry runway anyway), but that isn't why reverse isn't usually included in stopping performance charts. That's to do with aircraft certification rules.On a wet or icy runway, reverse thrust is much more significant especially compared to wheel braking.Kevin Hall

0:40 sec inhttp://www.youtube.com/watch?v=bFT0YO2CdM0FRED

The Hawker Siddeley Trident also allowed for reverse thrust to be applied before landing!!The VC10 having four rear engines is allowed to do a full start up before push back and consequently No's 1 and 4 engines are selected to idle reverse during push back to reduce jet blast!!vololiberista

So in the case of the NG assuming 27000 lbs of thrust at full throttle

I think you guys are seriously missing that during rev operation you will never ever go anywhere near 'full throttle', I'm pretty certain, not even mentioning many airports don't really like more than idle reverse anyways. Without getting into any numbers I would be convinced there is significantly less net thrust available during revs than fwd thrust operation, even with levers at full aft stop. Plus during A/BRK operation it simply reduces brake wear a bit and doesn't really change the actual braking or stopping distance, as the autobrake has its preset deceleration value.On a side note, but as already has been said above, if I remember correctly reverse thrust is not considered with landing performance figures since you need to be able to stop without having to use the revs (e. g. some of your engines could always have failed haha), and not because it simply doesn't add much to the braking effect. If small effects were not reflected in performance numbers you'd nowhere see something like "add 1% for BLEEDS ON" or the like (just making this up, but I guess you get the point).

0:40 sec in

That's insane. Thanks for posting! Look, you even see the hot air flow split up and turn fwd violently, haha... great! :(

Are yu guys factoring the ram drag of a NG with 140 KTAS so you can determine the net thrust output?any way, afaik, the 737 throttle has gates for reverse handle that gives you about 70%, 95% of N1 and full. Never knew a pilot that attempted to put full reverse thrust for no good reason (Good reasons: RTO, EMERG Land)

Can you deploy them in the air? (of course that would be bad :()

In NG yes, but is Idle Reverse only. RA must be at or bellow 10ft

The dc8 allow reverse thrust inflight as well

only Idle reverse and for the #3 and #4.

Hi,Some 737s were retro-fitted with beefed up landing gear, and were certified for reverse thrust at 50 ft. It was designed to get it into short runways in the jungle of South America (they would fly over the trees low and pull reverse; the landing gear would take the high vertical rate as it literally dropped in on the runway).Getting out wasn't a problem, but a standard approach over the trees would mean the runways were not long enough.Best regards,Robin.

Lol, nice one. But today isn't April 1st, mate.

There's plenty! Like some already mentioned earlier in this thread, I can add that it was apperently SOP on the TU154'sFRED

I think you misunderstood. He meant that on Boeing airliners and similar aircraft that reverse thrust is not controlled with the primary thrust levers but with dedicated reverse thrust levers. He was not talking about inflight thrust reverse capability.

any way, afaik, the 737 throttle has gates for reverse handle that gives you about 70%, 95% of N1 and full.

Sorry, but where did you get these numbers from?? :(

I think you misunderstood. He meant that on Boeing airliners and similar aircraft that reverse thrust is not controlled with the primary thrust levers but with dedicated reverse thrust levers. He was not talking about inflight thrust reverse capability.

Yeah, I did!

Sorry, but where did you get these numbers from?? :(

talking with two captains of 73G/738