# عندما يعطي الطيار all power للمحركات عند الاقلاع ترتفع مقدمة الطائرة بزاوية معينه ,طيب ماهو الجزء الذي رفع مقدمة الطائرة ؟؟؟

(RUF) #1

اريد جواب لسؤال التالي وهو عندما يعطي الطيار all power للمحركات عند الاقلاع ترتفع مقدمة الطائرة بزاوية معينه ,طيب ماهو الجزء الذي رفع مقدمة الطائرة ؟؟؟ ياليت تكون الاجابة مفصلة واذا كان هناك رامج محاكاة للعملية ارجو مساعدتنا فيها

(eng:amr) #2

Well, i’m not sure whether i got your question the right way or not, but i guess you were talking about how the nose of the aircraft is raised up from it’s initial position to a higher angle of attack during takeoff, if that’s what you meant, the answer would be so simple…

In all sub-sonic fixed wing aircrafts, there’s a very important component called “Elevators”, they’re mostly mounted on the Horizontal Stabilizer in the rear part of the fuselage.

The Elevators are likely airfoils, or in other word small wings, whom angle of attack can be varied, upwards or downwards.

Basically, the lift force produced by wings isn’t passing through the center of gravity, thus, it causes a moment tending to rotate the aircraft.

When the Horizontal stabilizers and elevators are in neutral, they produce enough moment to counteract the moment caused by the lift force, we do this when we want the aircraft to fly level…

But in case of upwards motion of elevators, which is our case, the elevators have a negative angle of attack, so, the resultant of the forces on both the upper and lower surfaces of it would be pointing downwards.

If you now imagine the aircraft as a rigid body, which has a force acting on it and have a distance from it’s center of gravity, that force would cause a “Moment” that would rotate the whole body in the rotational direction agreeing with it, i guess the picture would talk clearer…

After the nose is raised, the whole aircraft including the wings will be oriented upwards, thus increasing the angle of attack of the wings, and consequently increasing lift force that would take the aircraft higher and higher…

Still the aircraft won’t be able to raise its nose without high engine power, as the elevators won’t generate a force large enough to rotate the aircraft, until the air velocity on its surfaces reaches higher values, according to the simplified relation:

Force = 0.5 * (density) * ( lift coeff.) * (surface area) * B^2[/b]

And so we would need to set engines power to “Full Power” to gain horizontal speed quickly, so as to be able to raise the nose and consequently increase the wings angle of attack and consequently increase the lift generated to get the aircraft off the ground before the runway ends !

The whole story is reversed when you you want to drop the nose down, as shown in the picture too.

If you have any notices, or you basically meant another question , just let me know.

(RUF) #3

Thank You So Match Sair I Have Some Notices And I Will Tell You Later

(RUF) #4

أتمنى أن أتواصل معك في حل أو ايجاد حلول بعض المسائل التي لدي ويكون هنالك رسم توضيحي أو برامج محاكاة

(RUF) #5

THANK you sir I read your response and I will tell you what I am understand :
I am understand the small wings are basic part for takeoff
When the pilot give all power to aircraft after he is pull leash to some angle and the nose aircraft is raised and by motors the aircraft is able to takeoff force
:sm220:

(الطيار المنوفي) #6

بارك الله فيكم