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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 decel

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.

WalterBright 3y ago
> 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.
- Dalewyn 3y ago
  >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.
  - WalterBright 3y ago
    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.
- deleted 3y ago
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WalterBright 3y ago

> 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.

Dalewyn 3y ago
>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.
- WalterBright 3y ago
  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.
deleted 3y ago
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