Discussion:
777 bug with one engine out
(too old to reply)
legoboyvdlp R
2017-06-21 13:47:09 UTC
Permalink
Hey there,
I just checked out the 777 from
https://sourceforge.net/p/flightgear/fgaddon/HEAD/tree/trunk/Aircraft/777/
to ensure that this bug is not already fixed ;)

As reported in
https://forum.flightgear.org/viewtopic.php?f=17&t=32400&p=312883#p312883
when you cut one engine, it maintains high thrust, making it difficult or
impossible to slow down.

As a test, I took off from SVVP, climbed past 10000, then opened the
property browser to /engines/engine[1].
Here are the respective values for engine number 2, in FLCH and CLB thrust:

N1: 81.485
N2: 94.14
Thrust: 46800 lb approx

I then cut #2 engine, while in FLCH and CLB thrust.
N1 began to decrease. I continued climbing to 14000 which would be my
cruise altitude.

At that point the parameters were as follows:

N1: 0
N2: 0
Thrust: 41070 lb approx

I flew for about 60 seconds: the left engine's N1 had to be quite low
(~30%) to maintain 300kts. I then began to descend. Thrust on engine 2 was
stable at about 40800 lbs approx while N1 was at 0. When I began to
descend, the high thrust on No 2 caused it to be impossible to descend
without overspeeding at my weight.

Therefore, the 777 engine has a major problem with thrust and one engine
out. Jonathan
d***@mi7.us
2017-06-21 20:48:03 UTC
Permalink
Post by legoboyvdlp R
As reported
in https://forum.flightgear.org/viewtopic.php?f=17&t=32400&p=312883#p312883
when you cut one engine, it maintains high thrust, making it
difficult or impossible to slow down.
As a test, I took off from SVVP, climbed past 10000, then opened the
property browser to /engines/engine[1]. Here are the respective values
I then cut #2 engine, while in FLCH and CLB thrust.
N1 began to decrease. I continued climbing to 14000 which would be my cruise altitude.
I flew for about 60 seconds: the left engine's N1 had to be quite low
(~30%) to maintain 300kts. I then began to descend. Thrust on engine 2
was stable at about 40800 lbs approx while N1 was at 0. When I began
to descend, the high thrust on No 2 caused it to be impossible to
descend without overspeeding at my weight.
It has been my experience that the autopilot will control both/all
engines in any manner it feels is necessary unless that engine(s) has
been shut down. Reducing throttle on an engine (i.e.: 1, 3, or 4)
to flight idle will not stop the autopilot from commanding all engines
to the same throttle level or thrust level.

-- Dr. R0ckso, Ph.D.
w***@gmail.com
2017-06-22 01:05:15 UTC
Permalink
It has been my experience that the autopilot will control both/all engines in
any manner it feels is necessary unless that engine(s) has been shut down.
Reducing throttle on an engine (i.e.: 1, 3, or 4) to flight idle will not
stop the autopilot from commanding all engines to the same throttle level or
thrust level.
this seems to be a logic error somewhere...
--
NOTE: No off-list assistance is given without prior approval.
*Please keep mailing list traffic on the list unless*
*a signed and pre-paid contract is in effect with us.*
legoboyvdlp R
2017-06-22 14:45:37 UTC
Permalink
Post by d***@mi7.us
It has been my experience that the autopilot will control both/all
engines in any manner it feels is necessary unless that engine(s) has
been shut down. Reducing throttle on an engine (i.e.: 1, 3, or 4)
to flight idle will not stop the autopilot from commanding all engines
to the same throttle level or thrust level.
My point is that the engine maintains thrust at standard cruise thrust even
with the throttle to idle and the engine shut down.
Jonathan
Post by d***@mi7.us
It has been my experience that the autopilot will control both/all engines in
any manner it feels is necessary unless that engine(s) has been shut down.
Reducing throttle on an engine (i.e.: 1, 3, or 4) to flight idle will not
stop the autopilot from commanding all engines to the same throttle level or
thrust level.
this seems to be a logic error somewhere...
--
NOTE: No off-list assistance is given without prior approval.
*Please keep mailing list traffic on the list unless*
*a signed and pre-paid contract is in effect with us.*
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