Diego
Topic Author
Posts: 135
Joined: Mon Apr 23, 2001 7:33 pm

Derated To

Tue May 15, 2001 5:15 pm

Hi folks
Can anybody tell me why in the Derated Take off procedure you have to assume a higher temperature?
Regards Diego
 
JETPILOT
Posts: 3094
Joined: Tue May 18, 1999 6:40 am

RE: Derated To

Tue May 15, 2001 5:54 pm

I think your talking about the assumed temperature of 49C for reduced power setings?

Your assuming a higher temperature in order to reduce the power output of the engine.

You only used the assumed temp as long as the runway or second segment climb limit don't dictate a higher power setting, or the max reducable numbers aren't exceeded.

If the runway limited weight is less than the assumed temp limit you must use the temp for the runway limited weight.

Same story with second segment limits as previously stated.

Why 49C is used I can't answer that. I don't know how the yarrived at that temp.

I don't know if my ramblings helped any.

JET
 
F-WWAI
Posts: 129
Joined: Thu Dec 30, 1999 7:41 am

RE: Derated To

Tue May 15, 2001 6:11 pm

that's relatively simple.
imagine that your max take off thrust available depends on outside air temperature. it's flat rated (=constant) until a certain temp (e.g. ISA +15C) then decreases linearily with temperature to maintain constant turbine entry temperature.
given this, you may understand that you can take off a certain aircraft gross weight until a certain OAT. got it?
imagine now you are at low OAT but you have a GW which permits take-off at ISA + 40C. then you can tell you thrust control to compute the take-off thrust at the assumed temperature of ISA+40C, and you will obtain the thrust required for the take-off.
clear enough?
 Smile/happy/getting dizzy FW
 
JG
Posts: 165
Joined: Tue Jun 07, 2005 1:53 am

RE: Derated To

Wed May 16, 2001 4:27 am

Additionally, derated thrust and assumed thrust are two different beasts. The CFM powered 737's I used to fly could do both derate and assumed (also called balanced thrust) individually or combined. The 320 series I fly now simply uses assumed temperature. On our 320's that assumed temperature can be as high as ISA + 53C

Who is online

Users browsing this forum: No registered users and 12 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos