Simviation Forum - Flaps at high altitudes

May 26^th, 2004 at 9:30pm

rgenius Offline
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Hi there, im a newbie fs pilot; and i have this trouble flying 747's at high altitude. say im flying at 35,000 at .80M, my plane suddenly turns into a stall. im on autopilot.

i tried again but now i put on flaps at that height and it seems to stabilize the plane at 5 deg pitch-up. is this really what pilots do up there? wont it damage the flaps at that speed. or im just doing it wrong.

rgen

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Reply #1 - May 26^th, 2004 at 10:42pm

Nexus Offline
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Yes flaps would NOT like that Wink

Maximum flap extension altitude for the big Boeings is 20.000ft

The reason why you're stalling may be because you're just too heavy to fly M.80 at those altitudes. If an aircraft has to take off with full fuel loads it will use step climbs. It basically means that you fly to an intermediate flight level, then level off until you've burned enough fuel so you can continue the climb to a higher flight level and still maintain the same speed.

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Reply #2 - May 27^th, 2004 at 12:49am

rgenius Offline
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but still i can go up as high as 35k?
what is the suggested vertical climb/min for 747's? i may have done this wrong, because i placed it at 1k/min; that could have caused it to pitch so high.

other suggestions... Grin

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Reply #3 - May 27^th, 2004 at 4:31am

Ivan Offline
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vertical climb in the 747...

you need a step climb, start with leveling at 30000ft
VS rate at 2500fpm until at 25000ft while doing 280kts IAS

decrease VSI to around 1000 after passing 25000 and keep speed hold until you get to M.60 then switch to mach hold

when level go to M.82-.85
Dont go over 91%N1 RPM
Keep track of the N1 rpm and climb a few 100ft when it drops under 91%
maximum altitude you can get is around 45000 ft

Russian planes: IL-76 (all standard length ones), Tu-154 and Il-62, Tu-134 and An-24RV&&&&AI flightplans and repaints can be found here

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Reply #4 - May 27^th, 2004 at 8:17am

Nexus Offline
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Quote:

vertical climb in the 747...

you need a step climb, start with leveling at 30000ft
VS rate at 2500fpm until at 25000ft while doing 280kts IAS

decrease VSI to around 1000 after passing 25000 and keep speed hold until you get to M.60 then switch to mach hold

when level go to M.82-.85
Dont go over 91%N1 RPM
Keep track of the N1 rpm and climb a few 100ft when it drops under 91%
maximum altitude you can get is around 45000 ft

Why climb at m.60?
Just keep the 280-300kts or whatever unlil you reach mach-crossover altitude and then change to climb speed mach number. Should occure around FL260 - FL290.
Normal procedure.

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Reply #5 - Jun 20^th, 2004 at 4:59pm

jrpilot Offline
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Isn't the plane in real life controlled by autopilot with the FMC (when autopilot is on)....wouldn't the Boeing climb itself to that height with LNAV and VNAV?

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Reply #6 - Jun 20^th, 2004 at 5:24pm

Craig. Offline
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VNAV, but yes the autopilot does it usually. side note the 777 and 767 have very strict flap speed limits an overspeed on them will require extensive maintanence on them, because of this many airlines have lowered the speeds by 5 to 10 knots to avoid any chance of damage, so high altitude wouldnt be a good idea:)

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Reply #7 - Jun 20^th, 2004 at 5:39pm

Nexus Offline
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Quote:

VNAV, but yes the autopilot does it usually. side note the 777 and 767 have very strict flap speed limits an overspeed on them will require extensive maintanence on them, because of this many airlines have lowered the speeds by 5 to 10 knots to avoid any chance of damage, so high altitude wouldnt be a good idea:)

Same for the 737's, one some airlines they have decreases the flap 1 speed by 20kts (from 250 to 230) and flap 5 speed by 25kts(250-225)...cheap buggers Sad

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Reply #8 - Jun 20^th, 2004 at 5:40pm

Craig. Offline
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LOL arnt they just:)

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