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Based on my experience with jet transport aircraft, thrust reverser levers can only be engaged after reducing the throttle to idle. Do any jet-powered aircraft exist that can engage the levers at power settings above idle?

SMS von der Tann
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  • Define thrust reverser. – Jim Jan 21 '23 at 06:37
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    @Jim Thrust reverser is a mechanism that changes the direction of the thrust vector by approximately 180°, while preserving as much of it's magnitude as possible. – Aditya Sharma Jan 21 '23 at 23:59
  • More like 100-120 deg. The deceleration you get is fairly modest, and is not even included in stopping distance performance data. Basically considered a bonus. Almost all of your stopping power is brakes. Cascade style reversers are the worst. – John K Jan 22 '23 at 03:27
  • Most thrust reversers divert the flow about 90 degrees. Rather than reverse thrust, this eliminates the jet thrust -- leaving the rest of the engine as a tremendous drag producer. This reduces landing distance. They are omitted from performance data because you must still be able to land if the reversers fail. A few aircraft (including the C-17) turn the flow enough to truly reverse thrust. – Rob McDonald Jan 22 '23 at 05:17
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    @AdityaSharma - Yes. I was probing to see whether their definition covered things like thrust vectoring. – Jim Jan 22 '23 at 20:29
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    Are you only interested in "as delivered" or also in "after modification"? – BowlOfRed Feb 03 '23 at 00:23
  • Probable duplicate of https://aviation.stackexchange.com/q/3660/7532 I don't want to start the close-vote on it, because (as a mod) my action would immediately close it, and this is a reasonable vote for the community. But if somebody would nominate the question to be closed-as-duplicate, that would be great. – Ralph J Feb 04 '23 at 21:15
  • @RobMcDonald doesn't the engine still suck air in, creating forward thrust? – Someone Mar 07 '23 at 16:53
  • @Someone Thrust is $F_n=\dot{m}(V_j-V_i)$ proportional to the change in velocity through the engine (axial component). If the aircraft is moving forward, the $V_i$ will be similar to the forward speed. If the thrust reversers turn the flow (essentially bringing the axial component of speed to be less than $V_i$, then the $\Delta V$ term will be negative and you will produce a negative force. – Rob McDonald Mar 07 '23 at 22:10

2 Answers2

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There are no commercial aviation aircraft that are made this way. There are physical locks inside the throttle levers that make it impossible to raise the reverse thrust lever if the throttle lever is forward of idle.

Now, you say "any"...that's pretty broad. I'm not going to say there's never been some obscure, weird airplane no one's ever heard of that might have been designed like you're saying, but it's hard to imagine why any manufacturer, civilian or military, would think this would be a good idea.

Edit:

  1. The source is my own experience. I am personally familiar with a wide variety of commercial jet aircraft spanning several decades of flying them, and no manufacturer designs TRs like this. Just the opposite: just having a TR become unlocked when it isn't supposed to is a problem that requires immediate attention. If the TR actually deploys, the engine will be commanded to idle by the EEC; in some older designs before EECs, the throttle would actually slam back to idle.

  2. This question was already answered here almost 9 years ago anyway.

Chris
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  • Nice find on the duplicate question! – Ralph J Feb 04 '23 at 21:16
  • "some obscure, weird airplane" -- The heavily modified biz jet used by astronauts to practice landing the space shuttle needed a lot of drag in order to be appropriately brick-lick. I think it had the ability to deploy thrust reversers in flight. But that is certainly an obscure, weird airplane. – Wayne Conrad Mar 06 '23 at 16:29
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The C-17's reversers can be used to back up on the ground. The pilot must throttle-up to do this.

They can also be deployed in flight during a tactical descent. I believe the throttles are usually kept at idle during this maneuver.

Rob McDonald
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    DC-8s (if any are still flying) can use thrust reversers (on 2 of the engines I believe) in the air. –  Jan 22 '23 at 00:01
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    @757toga do they need to spool down to flight idle before engaging the thrust reverser mechanism? – Aditya Sharma Jan 22 '23 at 00:02
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    @AdityaSharma It is my understanding that the thrust levers have to be at flight idle. I've never flown a DC 8 so I don't know if there is a published spool down criteria before engaging the reversers. –  Jan 22 '23 at 04:28
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    @757toga sure, thanks – Aditya Sharma Jan 22 '23 at 05:43
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    This doesn't answer the question! There are many aircraft that can use reversers to back up on the ground as well as in the air. However, in all of those I'm familiar with, you first have to retard the thrust levers to idle, then engage the reversers, and then you can add thrust again (usually with the reverse levers). – Bianfable Jan 22 '23 at 11:32
  • @ Bianfable - any aircraft design that proposed allowing a pilot to engage thrust reversers without first going to zero throttle would immediately fail a host of FHAs, PSSAs and FMEAs. i.e. it'd be a fundamentally unsafe design which the regulatory authorities would correctly demand be amended. – Amiga500 Mar 07 '23 at 11:05