Weird underspeed issue?

[Dragonmount 5]

I brought this out of retirement for the first time in a very long time, and my one problem with this bird is that it will not stay at the FMC speed, it always flies well below, sometimes to the point of causing the aircraft to dip, and if you use RC4 like me you're going to get yelled at the whole flight. Is it because I was not at the optimal cruise altitude?

 

Patrick Boynton

[flibinite 18]

Need a lot more to diagnose, but to start suggest using the Load Manager to set, say, 2/3 load and 1/2 fuel, then take her up to 35,000 and see how she cruises.  Should be no problem,  Maybe take the tutorial flight over again as a refresher?

[Dragonmount 5]

This flight was at about 90% fuel and 1/3 passengers if that helps?

 

Patrick Boynton

[por930 51]

This flight was at about 90% fuel and 1/3 passengers if that helps?

 

Patrick Boynton

Hi Patrick, I think you maybe need to 're-position' her, and see how this goes...A flight of say 2 hours, 1/3 fuel, 0 pax, minimal cargo. When you set up the flight in the FMS, pay attention to the speeds set up for the flight and verify to see if she achieves them or where she starts to 'go slow'. Check your weather program to see that the temps are not crazy high at cruise altitude. With this sort of load and minimal fuel, she should be like a rocket and easily cruise at FL350

I recently brought mine out of the hanger last week after several months. Must say, I needed the tutorial again, as very rusty and this reinforced the set up required, as very different to the Boeing and the Airbus.   

[Dragonmount 5]

Is there a better load than 0 passengers? I like having some weight on the plane. 

 

Patrick Boynton

[pcubine 143]

Anytime I have had a problem like this, it has always been the OAT/TAT being incorrect. I would be flying along in the MD-11F at FL300. Suddenly the TAT would go from -8C to +22C. The altitude would stay the same but the speed would start to decrease until I had to go to VS and start descending to maintain a reasonable speed. In 15-20 minutes the TAT would go back to -8C and I could start climbing again and when level at FL300 accelerate to normal speed. It was a problem with Active Sky X and AS2012 at certain waypoints. HiFi corrected the issue and the OAT was okay in AS2012 and ASN. The MD-11F was at 160000 lbs. of cargo and close to maximum fuel for a 12 hour flight.

[por930 51]

Is there a better load than 0 passengers? I like having some weight on the plane. 

 

Patrick Boynton

Can be anything. I was just trying to make the load so light, no chance of a weight issue. If you put in 20 vip's, Will still be super light....

 

I just saw the post by Michael. I agree with him. Temps at cruise some times climb to too high unrealistic temps, which will force your speed down, hence altitude. Depends what weather program you used

[Dragonmount 5]

I think I will redo a flight, but shorter, I had intended this to be my first long haul flight in ages, but maybe some experimentation is needed.

 

Patrick Boynton