Timeline for Why does "V1 increase with decreasing density"?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 21, 2020 at 20:00 | comment | added | Bianfable | @AnasMaaz I know. I'm not suggesting brake temperature makes no difference. I'm talking about the effect of different densities on the brakes. And AFAIK air density has essentially no effect on the force the brakes can deliver, but maybe I'm wrong about that. | |
| Dec 21, 2020 at 19:40 | comment | added | Anas Maaz | It does. It does a lot. I have been an airline pilot for many years now and I see this everyday. Brake temperature has a massive effect on the take off performance. The main reason why A320 has brake fans is to reduce turn around time. | |
| Dec 21, 2020 at 18:23 | comment | added | Bianfable | @AnasMaaz I agree, but the ambient temperature should not have a large affect on the brake temperature. The increase in brake temperature is proportional to the amount of energy absorbed by the brakes and therefore proportional to the aircraft kinetic energy. | |
| Dec 21, 2020 at 17:38 | comment | added | Anas Maaz | @Bianfable Not correct. Heated up brakes cannot be as efficient as cool brakes. Vmbe is the speed on the ground at which an aircraft can safely stop within the energy capabilities of the brakes. Above this speed, even if you apply the maximum amount of 'braking force' the brakes cannot safely stop the aircraft. | |
| Dec 21, 2020 at 17:32 | comment | added | Bianfable | @AnasMaaz The force from the brakes will be the same, regardless of density. The max. brake energy is limited by the kinetic energy of the aircraft, which depends on (ground speed)^2, but Vmbe is given in indicated speed, not ground speed. So the value will change with density, but the braking force and total kinetic energy limit will not. | |
| Dec 21, 2020 at 17:13 | comment | added | Anas Maaz | 'Now, at lower density, the thrust T will decrease, but the brake force Fbrake will be unaffected.' May I ask how this is possible? With reduced density, the maximum brake energy speed reduces. The brakes becomes more inefficient. | |
| Dec 21, 2020 at 15:51 | vote | accept | Darshan Patil | ||
| Dec 21, 2020 at 15:50 | comment | added | Darshan Patil | That edit makes it much more understandable, appreciate your effort and time ! Good day @Bianfable | |
| Dec 21, 2020 at 15:47 | history | edited | Bianfable | CC BY-SA 4.0 |
add explanation of forces
|
| Dec 21, 2020 at 15:39 | comment | added | Darshan Patil | But why would you say that accelerate go distance would, increase more that accelerate stop distance? Is there something I'm missing ? Is it a parametric thing? | |
| Dec 21, 2020 at 15:32 | comment | added | Darshan Patil | If both curves move upwards, wouldn't the net V1 decrease ? | |
| Dec 21, 2020 at 15:20 | history | answered | Bianfable | CC BY-SA 4.0 |