De rated thrust takeoffs.

[Zadil Lucas]

Hi folks,

For the MD-80 drivers, what is the maximum assumed temp one could/should set for takeoff? I know it depends on runway length, aircraft weight and other factors. Is it also true that you may sometimes have a lower takeoff EPR depending on the assumed temp used, than that used for the CLB? It's been many times that I believe I heard a aircraft perform a de-rated takeoff, and heard it power up during the initial climbout. At least I can hear this with most aircraft. The DC-9's, 727's and 737-200's sound as if they are using full power all the time. Then again some of the older MD-80's are loud on the takeoff as well.

What is the target EPR used when spooling the engines for the takeoff? I heard 1.4 EPR is usually the EPR reached when standing the throttles up. Last but not least, why do the MD-80's taxi with flaps 15 set after landing? I've seen this on a MD-80 checklist and wondered why. I've also seen it in practice at EWR. Of course, the crew's raise the flaps all the way up prior to docking but why not do that soon after the landing like most other aircraft?

Sorry for the amount of questions but you won't know if you don't ask. I've also been a keen "watcher" of the forums for awhile and figured I could get a good answer from here.

Thanks in advance

50 above and at 220 decide...LAND

[mutt]

Max Derate, I would guess that it's ISA+45C.

Mutt.

[StressFree]

DH,
On the MD-80 series de-rating is achieved by using an assumed temperature, known as a 'flex' take-off. The maximum assumed temperature that may be used is 50c. You could in theory have a slightly lower take off power than climb power although the difference would, I think, be unlikely to cause a noticeable increase in noise to an observer on the ground. The transition to climb power happens at 1000'AGL.
The reason for taxying with the flaps set to 15 degrees after landing is to provide enhanced protection from FOD damage to the engines. The extra protection is small but it could be the extra 5% thats stops a large stone from going into the engine.
I flew an MD-87 for 6 years and found it a really reliable, fun plane.
If you want to know more - fire away!!!! :D

[Zadil Lucas]

Mutt & StressFree

Thanks for the replies fellas. I never would have guessed that having the flaps set at 15 after a landing was a precaution against the infamous FOD. It makes a lot of sense now that I think of it.

As for the questions I have dancing around my head, there are a couple more. Here's a few:
What is the normal cruise speed for a 800nm trip if departing on time? I would say Mach .76 but I could be wrong. I know weight, in flight spacing and other factors apply, but what would be the ideal cruise speed? If departing late (an hour or more) what cruise speed would normally be used to make up for lost time?

Also, let's say you have a nice tailwind at your cruise alt, would you lower you cruise speed due to increased boost in ground speed? For example normal cruise speed mach.76 instead use mach.75/74. I suppose the normal thing to do would be to save the fuel and let the wind push you along.

Finally, what is the normal climb profile used when able to accelerate pass 250kts for the normal climb speed? For example 310kts/Mach .75 climb. What would the norm be for the descent?

Thanks guys in advance. I love the heavy metal and I like to learn the details and "magic" that get's tons of metal, plastic, fuel and "souls", up, up and away..

DH"

"WINDSHEAR. WINDSHEAR"