Take off and landing aside, can you properly control the aircraft on the ground without brakes? I'm thinking of stopping at hold short lines, at the gate, etc. How precise, responsive is reverse thrust in those cases?
Or will they get picked up by those little cars and pulled right after landing?
It's not very responsive at all. Nor is it meant for this purpose. It's just a brake assist for use on the runway.
Also, reverse trust is hard to maneuver with considering you will immediately start reversing once you've stopped moving. Unlike a brake that has a stop as an "end state". If they really start taxiing using that it'll lead to collisions at least, I'm sure, because of unintended reversing.
It's a harebrained plan as presented here IMO.
But perhaps it's more nuanced? Just not using the brakes unless you really need them? This is what we used to do at the gliding club too, since brake pads are expensive and our runway was 5x the length needed for an unassisted rollout.
I don't think the margins are ever that high on airliners though... It still sounds very dangerous and has the risk of pilots getting confused.
My thoughts as well: go through the crazy "look ma, no brakes!" emergency routine for landing and use the remaining pads for taxiing. Not an aircraft engineer, but my guess would be that the pad wear for one regular landing would be good for a decade or two of what's consumed during taxiing.
(and when the inevitable accident happens, the victims' suffering will at the same time be acclaimed as heroic sacrifice and a called out as a direct attack by "evil nato, how dare they not give us what we need for business as usual". Chances are less people will die for this propaganda stunt than in the apartment bombings)
The thrust reversers are more than just an assist on the runway. You can land without the reversers, but I'm pretty sure you'll have to go get the brakes replaced before it's ready to fly again. It'll also consume a dangerous amount of the runway.
The reversers are no joke, especially when the aircraft is heavily laden.
An aircraft operating nominally is designed and intended to be able to land safely relying on just the brakes. Thrust reversers are also used because they decelerate the aircraft quicker and with less wear on the brakes, aka thrust reversers are used out of convenience and benefits.
Thrust reversers may be used solely in an emergency that renders the brakes inoperable, but such situations are so exceptional they aren't useful for any general observations.
An aircraft that can't land safely with just brakes would not be certified to fly.
> An aircraft that can't land safely with just brakes would not be certified to fly.
Yes. That doesn't contradict what I wrote.
The thrust reversers also greatly reduce the stress on the tires, another critical and expensive item. There's also the enormous heat generated, which stresses the rest of the landing gear and the bearings.
One of the certification tests is the airliner is landed with flaps up, at max landing weight, and no thrust reversers.
The tires inevitably blow and catch fire, and the airplane literally grinds to a halt, with a raging fire on each truck. The firemen have to wait a specified amount of time before they can put the fire out.
While this is "landing safely", at minimum the landing gear is wrecked, and I suppose some of the fuselage panels.
The thrust reversers are an expensive piece of machinery, with a lot of engineering expended on them. They are not a "would be nice if" piece of equipment. The brakes are a backup system for the thrust reversers, not the other way around.
>The brakes are a backup system for the thrust reversers, not the other way around.
Absolutely *NO!*
Thrust reversers are always supplementary to the brakes, the brakes are always the primary means of bringing the aircraft to a stop on the ground. If the tires blow, the brakes burn out, and the landing gears are a goner in an emergency landing then so be it, that is all part of the design specifications.
Why is it like this? Well what happens when the aircraft loses all engines? This has happened many times, and far more frequently than failures concerning the brakes. If an aircraft is not designed and certified to land safely with just brakes, it means an aircraft with all engines out can't land safely. That is absolutely unacceptable.
Incidentally, plenty of flights land nominally without using thrust reversers depending on the situation. Using them is preferred because the brakes are worn out less and the aircraft spends less time on the runway, but if the pilot in command appropriately decides to land without thrust reversers that is still perfectly safe without any of the fireworks.
Thrust reversers are marvels of engineering, that is never in doubt, but they are never the primary means of stopping an aircraft.
As I mentioned, the aircraft is certified to land safely with just the brakes.
The cert test that results in flames is a worst case scenario - in particular, with flaps retracted, the airplane lands at a much higher speed than normal.
And, of course, when you're taxiing around, you'll just use the brakes.
I suspect they can still use them in those situations, since there is very little wear just holding still.
The planes probably still have brakes, just the pilots are told not to use them when landing - this would make them last much longer, but still be available.
Not at all. Thrust reversers, depending on engine model, can take a few seconds or more to engage, and the engines themselves can take even longer to spool up thrust from idle or to spool down when no longer needed.
I'm guessing that the vast majority of brake wear occurs during landings, so re-enabling them for taxiing and at the gate would still save a whole lot of pad.
This. Breaking from 30km/h wears brakes much less than from full landing speed. A policy of just using thrust reversers more generously would save quite a bit of brake life.
Or will they get picked up by those little cars and pulled right after landing?