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lh777

Initial climb performance

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After taking off at 1500 ft (rad alt) I start to retract the flaps and reduce the EPR to the value of climb trhust compared to the RAT.
With takeoff weights less than 230000 lbs, I always set the plus an EPR value of 1.55 (RAT 35).
Although this represents one of the lowest thrusts, to maintain 250 kts with 0 flap, I get climb rates of at least 4000 ft / s.
Is it correct to have such high climb rates?
For low take-off  weights, are there procedures for de-rate the climb trhust?

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230,000 lbs is very light, so it's too be expected there will be a high rate of climb. 

 

The performance charts I used didn't have figures for de-rated climb or takeoff.  However, I think I might have some that do -- give me a little time to look for them,  I just returned from a short vacation and have a lot to get caught up on.  

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On 7/27/2019 at 5:27 PM, lh777 said:

After taking off at 1500 ft (rad alt) I start to retract the flaps and reduce the EPR to the value of climb trhust compared to the RAT.
With takeoff weights less than 230000 lbs, I always set the plus an EPR value of 1.55 (RAT 35).
Although this represents one of the lowest thrusts, to maintain 250 kts with 0 flap, I get climb rates of at least 4000 ft / s.
Is it correct to have such high climb rates?
For low take-off  weights, are there procedures for de-rate the climb trhust?

 

DC-8's were hotrods, especially when unloaded -- in testing one of them broke the sound barrier -- the first civilian airliner to go supersonic, beat the Concorde by several years.

 

I have de-rated the aircraft on takeoff when light, but, I didn't have any resources for correct EPR etc. for that.  I just guessed, my luxury as a sim pilot.  If Michael can find some info on de-rate that would be nice.

 

 

 

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I looked at my manuals and there is a set of tables from American International Airways that include a reduced takeoff power chart.  You can find these online if you look.  I don't want to reproduce possibly copyrighted material on the forum.  However, the chart in question references another chart necessary to calculate an assumed temperature that isn't included, so it is not really useful.

 

I also have a Buffalo Airways manual with a similar "standard" in addition to maximum takeoff thrust table for the 61 series aircraft which use the same engines as the 50 series.  This also requires use of additional charts corresponding to specific runways, which I don't have, to calculate an assumed temperature, so again not really useful.

 

Neither manual contains any reference to reduced climb power, only takeoff. 

 

My United manual doesn't reference reduced power at all. 

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I don't know if this helps you or not, but Assumed Temp is automatically calculated in our Airbuses after you enter the various data.

 

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SAS DC-8-60 had JT3D-7 engines with static takeoff thrust at sea level of 19000 lbs  (8620 kp)

 

No reduced climb power only de-rated takeoff power.

 

I take a chance to add a page from AFM DC-8 SAS

IMG_20190828_0001.pdf

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