When I try to fly with the Boeing 747-8, even with the lowest weight settings applied and at maximum throttle, after takeoff at 15.000 to 20.000 feet the airplane struggles to maintain certain speeds and usually stalls. I’ve been having this issue since I started flying with the Boeing 747 and I couldn’t find anybody thats has the same issue. There’s also the same issue on the Boeing 787. Could someone help me fix it? Thanks
Make sure you are maintaining 250 knots below 10000 feet. Once above that set speed to 320 and climb so you maintain that speed, make sure you reduce your rate of climb (vs) to keep the speed up, at 30000 reduce to mach 0.82 and climb to your target hight.
People get into trouble because they speed is too low to continue the climb.
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Always keep in mind your climb rate is determined by speed and not pitch. You keep the speed and adjust the pitch.
What have you got in the way of a flight plan? I’ve been flying the 747 quite a bit lately and using simbrief to set not only the flight plan but also the weight and balance. Before I knew how to do the weight and balance parts (INDEX, SETTINGS, WEIGHT AND BALANCE, SET FROM OFP) I was having issues controlling it as the centre of gravity was all kinds of strange having set the aircraft from the world map style weight and balance screen
What speeds are you trying to climb at? Depending on weights set - 747-8 would quite happily climb at around 320kts indicated until passing around FL275 or even higher depending on outside air temperature, then as plane climbs into thinner colder air you transition to constant Mach number. As you climb to higher levels on constant Mach number - your indicated airspeed will start to decrease until it reaches critical Mach number (some times referred to as coffin corner) beyond which the airplane will stall.
In all Jets - speeds in climb is controlled by pitch, If flying manually - climb power is usually set and then pilot changes pitch to maintain airspeed. If flying on autopilot - VNAV will usually manage this very accurately. If using other modes then I would normally climb with FL-CH (flight level change) selected. You can also use V/S (vertical speed) however in vertical speed the autopilot DOES NOT take airspeed into account. For instance you could select V/S +2000ft for climb - Autopilot will continue to maintain that V/S even if your airspeed drops to below stall speed.
I’m also going to state the obvious here which isn’t always obvious to someone who has just started flying airliners
Your indicated airspeed is calculated as the difference in pressure between the static port and the pitot probe. As you get higher, air pressure drops and with it, your indicated airspeed. At cruise altitude of 36000ft, your indicated airspeed might only be 260kt compared to the 300+ kts that you had down at 15000ft but your ground speed will be nearer 460kt
That’s why Mach number becomes what is used above 20000 as that it your speed relative to the speed of sound and remains constant through increasing altitudes
So it might look like you are losing airspeed when you are not