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Most of the time the usage of reverse thrust is not needed. I wonder if it's an authority (e.g. FAA) requirement to land safely.

Obviously, in bad weather conditions or when the runway is contaminated, the brakes might not work as effectively and thus R/T may be required to land safely. However, in most of other situations the aircraft can brake OK. Given that it would probably be more efficient to land without using R/T, why don't airlines routinely do so?

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    $\begingroup$ Related, and should answer the question: aviation.stackexchange.com/questions/24629/… $\endgroup$ – Peter Kämpf Mar 5 '16 at 18:51
  • $\begingroup$ NO!!!! This is NOT a duplicate of those questions! Those are "engineering" questions about reverse thrust and the other ways to stop the aircraft; this question is asking about POLICY and (ultimately) the HUMAN FACTORS behind that policy. Not the same question, and not the same answers! $\endgroup$ – Ralph J Mar 5 '16 at 19:11
  • $\begingroup$ The question is, "why do comercial pilot always engage R/T"? That's a matter of policy. The point that it is often unnecessary is entirely valid, and at most the links to the other questions simply support that statement. WITHIN the body of the question, the (essentially rhetorical) question "wouldn't it be more efficient..." is answered in those questions, but the POINT of what's being asked is, given all of that, why do pilots always use R/T anyway? And THAT question isn't addressed elsewhere as far as I can tell. Everything else simply supports that "why" question. $\endgroup$ – Ralph J Mar 5 '16 at 19:37
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The correct answer is, habit patterns.

If your habit, as a pilot, is to ALWAYS select reverse thrust, you'll do so reliably even when the weather is bad, you're fighting gusty crosswinds, and there is whatever else going on. On the other hand, if you sometimes do & sometimes don't select reverse thrust, that habit pattern isn't there to back you up when you have the proverbial "dark & stormy night" and getting into reverse thrust right away may be the difference between staying on the runway or running off the end.

For example, if I'm landing a fairly light aircraft on a 12,000' dry runway in DEN with a little headwind, it is entirely possible to leave the thrust reversers stowed, roll out with the speed brakes deployed, tap the brakes slightly, and exit on the last high speed taxiway at a normal taxi speed. And I'd burn less fuel and make less noise doing that. But at my carrier, I'm not allowed to, because it's considered that the habit pattern of always deploying the T/R is so important that it's worth it to burn that extra gas even when it isn't strictly necessary, so that on the day when it's vital, the habit pattern to grab the T/R's right after touchdown is strong.

I don't think that this is an OpSpec (i.e. FAA) requirement, at least for the aircraft that I fly, but I'm quite certain that it is a requirement in our books, so my supposition is that it's a company requirement. If that assumption is correct, then other companies might choose to do differently (and I recall one early morning arrival into Frankfort on a Lufthansa A-320 that used NO reverse thrust, but some heavy braking instead -- presumably to reduce noise at that hour of the morning). The fact that safety is so important, though, probably drives plenty of operators to make the same choice that our carrier does: build the habit of ALWAYS using reverse thrust -- even though that means sometimes using it when it isn't necessary.

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  • $\begingroup$ I very much agree that deploying the reversers as soon as possble is a good habit pattern. However, perhaps it should be noted that because you deploy them doesn't mean you have to use other than idle thrust with them deployed. Deploying bucket style reversers but staying at idle power gets you a fair amount of drag while the airplane is still at high speed right after touchdown. This is what we typically did at the two 747 carriers I worked at when we had a long runway and had no need to turn off earlier than that allowed. $\endgroup$ – Terry Mar 5 '16 at 20:42
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    $\begingroup$ Excellent points. Our policy is to deploy the reversers to at least Detent 2, which is beyond idle power, and our engines use sleeves rather than buckets. Again, desired habit patterns. Of course, they don't say how long we have to stay in reverse, so you could coast down to the last highspeed exit after stowing them. Each operator writes their own rules in that regard, and I'm not claiming that ours is optimal -- just mentioning what it is. The buckets-out+idle sounds like an excellent solution as well. $\endgroup$ – Ralph J Mar 5 '16 at 21:20
  • $\begingroup$ Thank you for such a good answer, that was what I was trying to know @RalphJ $\endgroup$ – Airman01 Mar 6 '16 at 10:00
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    $\begingroup$ Also perhaps worth noting that the extra gas to deploy TR's, even over a few hundred landings, is still a heck of a lot cheaper than writing off an airframe on that one time you do dump your brand new A380 off the end of the runway. $\endgroup$ – Jon Story Mar 7 '16 at 11:27
  • $\begingroup$ Could it also be to protect against a break failure? If you suddenly lose break power, the last thing you want is a delay while the thrust reverser deploy and activate. By deploying them in advance, you have them armed and ready if needed. $\endgroup$ – Gavin Coates Mar 7 '16 at 12:12
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How do you know it wasn't necessary?

  • Maybe there are planes in the pattern ready to land immediately after you. Delaying clearing the runway could effect the safety and schedules of dozens of other aircraft.
  • Maybe your brakes or tires are going to fail partway into your braking leaving you no time to use reverse thrust
  • maybe a portion of the runway IS contaminated. The only way to avoid it is to slow as soon can. The longer you are at high speed the more likely a problem like this will effect you
  • Something (another plane or animal) might encroach on the runway while you are slowing down lackadaisically
  • Wind or other weather phenomenon might effect your high speed landing roll. The period of time when a plane is near flight speeds while touching the ground is one of the most dangerous times in a flight. Many bad things can happen while "fast taxiing"
  • Missing an earlier taxiway might result in a longer taxi that's even more expensive than a little thrust reversal.

The danger level is so elevated, there is just no reason good enough to maintain high speed while on the ground, other than when you intend to take off.

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How can we say that it's not necessary?

I'd say that the reason I use reverse more then brakes is that it's my airline procedure and Airbus says that too!

Use of brakes to slow down airplane after high speed landing is not good for tyre's health. So what we do normally is slow down the airplane by thrust reversers till 40-60 knots and then we use brakes.

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    $\begingroup$ This doesn't seem to add anything additional from the two answers that were already posted $\endgroup$ – Greg Taylor Mar 6 '16 at 12:33

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