Full Thrust- When Is It Used

[BAe 146-100]

Hi,

I was wondering in what situation would you need to use full power for a take off?

Thanks :D
BAe 146-100

[Pub User]

Depends what you're flying.

My mate uses it every time in his HS125.

Another mate would only use it if an engine failed in his B757.

[Mad (Flt) Scientist]

It somewhat depends what you mean by "use full power".

Some airframe/engine combinations have a feature whereby the rated power following an engine failure is higher than that AEO. Following an engine failure, with the throttles in the take-off power position, then remaining engines will increase thrust to the "emergency"/OEI max thrust position.

In that case you could say that max thrust is only ever used following a failure of an engine. However, this operation is automatic and transparent to the pilot.

The only circumstances when take-off thrust should not be set with the throttles is when performance information is available for takeoffs at other than the rated takeoff thrust. If information is available then a 'flex' or reduced thrust may be used, where the thrust is reduced to conserve engine life at the expense of reduced performance. Since the reduced performance must not be allowed to infringe the certification performance minima, data is required (from OEM or other similar source) before the thrust is played with. In the absence of such information, only the rated TO thrust can be assured to give adequate performance.

[BAe 146-100]

Hi,

Thanks for your reply's :ok:. When a aircraft is empty or on a positioning flight would they use reduced thrust on take off?

Thanks
BAe 146-100

[Capt Claret]

Full thrust varies with airfield elevation and temperature. On the 146 fleet I operate, we use rated thrust in the following circumstances:

Once a week to confirm that rated thrust is achievable,
When the runway is wet,
If the crosswind is greater than 25kt from 55° or more off the runway bearing,
If the BRW is such that for the given airfield elevation/temperature/climb gradient required/TODA/TORA combination, there is no scope to conduct a flexible (reduced) thust take-off,
If the Captain/crew believes rated would be best, for example turbulence expected in the take-off flight path,
3 Engine ferry flights, which are operational crew only positioning flights.
On all other occasions we use Flex Thrust.

[pigboat]

Pub User, which model 125 does your friend fly? The 700 series had something called APR - Automatic Performance Reserve. On a maximum effort take-off, you armed the APR and it gave you 105% of N1 on the good engine in case of an engine failure.
(At least I seem to remember that's how it worked. I never flew the 700, only the -1AR):D

[Pub User]

I'm not sure which version 125, it's the RAF one. I confess I was being simplistic about the power used, but he pushes the thrust levers fully forward for take-off.

[pigboat]

Pub User, I think the RAF operated both the 1A's and the 600 series, both powered by RR Vipers. I think they were called the Dominie. The system I mentioned was fitted on the 700A and B series, both powered by the Garrett TFE731's. The 1AR's and the 400R series were retrofitted with the same engines but had no need for APR, since they weighed about 5000 lbs less than the 700.:ok:

[extreme P]

Use full thrust on a conaminated runway, windshear reported, MEL item such as a locked out brake etc.
Don't be so sure an engine failure in a 757 will automatically require full thrust. Reduced thrust assures a safe departure in regards to climb gradient. Jamming full thrust on only makes for more work controlling the rudder.

[CrashDive]

In general, on a B737 (300/700), we are obliged to use 'rated thrust' whenever:

- Runway is contaminated or slippery
- Marked temperature inversion or windshear
- Antiskid OFF or inop
- Either thrust reverser is inop
- PMC is OFF or inop
- Any power setting instrument is inop
- An RTOW table is not available.
- The aircraft performance calculation requires that we use it ( somewhat obviously )

In all other instances ( including departures when LVP's are in force ) we will use an 'Assumed Temperature Thrust Reduction' technique ( which is not the same as a 'de-rate' ) but only down to the point where the reduction is <= 25% and / or the engine becomes 'flat rated' biased to which ever is the most limiting ( i.e. which ever of these two provides the most thrust ).

[BAe 146-100]

Hi,

Thanks for your detailed replies :ok:.

BAe 146-100