Archive > Technical discussions
Help with Airbus 320-200
EHM-2198 Didimo:
A couple of days ago I flew the the main fleet's A320 for about an hour. I just took off from MPTO on the active runway (offline flight) with default fuel (full I think) and default cargo.
It flew beautifully, I took it up to 25000 en route to Limon, Costa Rica and did various maneuvers. I was able to step wise push the speed to nearly 320 knots IAS and perhaps a little bit more, anyway M0.80 I remember.
Being satisfied with it I decided to take the bird on an official flight from KATL to MPTO thinking that at that speed (M0.80) I could arrive in 3:30-4:00 hours (as in real life).
I started with 27000 pounds of cargo after lowering it down. In any case the default config was a bit off balance (COG forward). I loaded some 30000 pounds of fuel.
Well, to my surprise now I am right now at 33000' and in the past 2 hours I have not been able to push it past 220 KIAS without overspeeding :(
At this moment it is flying on this configuration:
- Airspeed 218 KIAS 9on the PFD vertical strip)
- Winds 093 degrees /09 knots
- Heading 182
- Ground speed 331 Knots
- Autopilot ENABLED
- Autothrottle ENABLED
- AP Speed: 218 ENABLED
- Altitude 33000'
- Pitch trim 2.8-3.0 (controlled by autopilot)
- Fuel On Board (now) 17940 pounds
In other words it should be the most fuel efficient mode, auto and at high altitude.
I don't know whether starting to dump fuel or what, at this speed the sun will rise and I will have to go to work.
Any ideas what I am doing wrong?
EHM-2155 Mariano:
Mate as you climb higher, the mach numbers are easier to "achieve" so, at 270 and 320 kts being m0.8, and 330 at 220 being 0.8, sounds about right... Check your ground speed it should be around 400 kts.
EHM-2198 Didimo:
Well I am at FL330 with the speed indicator at 218 which is what I set as target speed on the autopilot. The tape shows M0.57 as the speed and not M0.8
EHM-2155 Mariano:
That is definetly weird, what happens if you set your AP to mach mode and push it to 0.78?
EHM-1749 Hector:
Strange indeed. At FL330 and 218 KIAS, provided standard temperature rates, M should be 0.63 and the KTAS 364.
This link can help to understand how M varies with altitude:
http://www.hochwarth.com/misc/AviationCalculator.html
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