One (ok, many!) for the pilots, inspired by a post by
KeaneJohn in the NEO thread about rejected take off tests.
Presumably at their simplest these tests are what they sound like, namely can you safely halt the aircraft from some defined maximum speed (above which I guess you are taking off whether you want to or not....)
I would surmise that they need to do these tests with the aircraft at MTOW since that would affect braking distance? Do they just use ballast instead of pax and cargo? What do they do in respect of fuel load - on one hand, I can see that there could be benefit to running minimal fuel, as a risk mitigation strategy in case the test goes wrong. On the other hand, presumably a full fuel load more accurately represents the weight distribution and actual state of the aircraft in the event of a 'live' rejected TO?
From what I've read, such tests have to be conducted on the brakes alone, i.e. without assistance of any thrust reversers etc? I suspect passengers - including myself - probably overrate the importance of such additional deceleration, not least because it looks dramatic
If it can be quantified, what proportion of total available deceleration is due to the brakes?
How fast can brakes alone decelerate an aircraft, and is there significant differences between say an A318 and an A380. Naively I would expect there to be so, but perhaps the big lad simply has much more braking power to counteract the weight? (but then would it run up against limits of tyre friction?)
Lastly, in the case of real rejected TO, where the pilot can make a subsequent attempt, how do they ensure that the systems are in a state where it is safe to do so? Are there sensors, or do they make visual inspections? (I'm thinking for example, where the case of the first rejected TO has "cooked" the brakes to the point where their performance is dramatically impacted, I presume you can't simply "have another go" since if another rejection was needed, the brakes would not be able to stop the aircraft).
Lot of questions, so thanks in advance for any insights.