Simviation Forums

I was watching on kingschools.com a crosswind takeoff of a Cessna 172 I think so I understand that ailerons have to be applyed into the wind during takeoff. But there's something I don't understand.

1. I tought that no aircraft, and even a Cessna 172 which weights about 2000 lbs with fuel and crew cannot be pushed by the wind while the tires are on the ground, even if the aircraft is moving. So how is it possible? This is how I understand it. Let's use a Cessna 172 for example. If he's standing still on the ground the wind cannot push it because 2000 lbs or even 1600 when he's empty is too much for a wind, unless it's a hurricane, right? As soon as he starts the takeoff roll the wings starts producing lift and the weight on the landing gears is reducing so now the wind has a lower weight than 1600 lbs which it CAN push. Is this how the wind pushes the aircraft during takeoff?

2. If that is how the wind pushes the aircraft during takeoff, then it would be possible that the wind can push even bigger aircraft like a Boeing 737 which weight about 130000 lbs. He is much, much heavier than a Cessna 172 but he also has bigger wings which again reduce the weight on the landing gear during takeoff. So would it be possible the wind to push a heavy aircraft like a Boeing 737 after he speeds a bit and the wings start producing lift during takeoff roll? I think that in FS2004 the wind can't push heavy aircraft, only light aircraft. How do pilots deal with this, the same as with a Cessna 172, aileron in to the wind, in RL?

I was watching on kingschools.com a crosswind takeoff of a Cessna 172 I think so I understand that ailerons have to be applyed into the wind during takeoff. But there's something I don't understand.

1. I tought that no aircraft, and even a Cessna 172 which weights about 2000 lbs with fuel and crew cannot be pushed by the wind while the tires are on the ground, even if the aircraft is moving. So how is it possible? This is how I understand it. Let's use a Cessna 172 for example. If he's standing still on the ground the wind cannot push it. As soon as he starts the takeoff roll the wings starts producing lift and the weight on the landing gears is reducing so now the wind has a lower weight which it CAN push. Is this how the wind pushes the aircraft during takeoff?

2. If that is how the wind pushes the aircraft during takeoff, then it would be possible that the wind can push even bigger aircraft like a Boeing 737 which weight about 130000 lbs. He is much, much heavier than a Cessna 172 but he also has bigger wings which again reduce the weight on the landing gear during takeoff. So would it be possible the wind to push a heavy aircraft like a Boeing 737 after he speeds a bit and the wings start producing lift during takeoff roll? I think that in FS2004 the wind can't push heavy aircraft, only light. How do pilots deal with this, the same as with a Cessna 172, aileron in to the wind, in RL?

Essentially yes, although its more of a weather cocking effect than a comlete lateral push. You have to remeber almost all aircraft have a huge sail on the back (the fin). In larger aircraft this in some ways accentuates the effect. It is countered in exactly the same way though, using into wind aileron and judicious use of the rudder.

Essentially yes, although its more of a weather cocking effect than a comlete lateral push. You have to remeber almost all aircraft have a huge sail on the back (the fin). In larger aircraft this in some ways accentuates the effect. It is countered in exactly the same way though, using into wind aileron and judicious use of the rudder.

Ok, so crosswind can affect big aircraft on takeoffs. But is my "theory" correct? About how can quite weak wind of 10-15 knots push aircraft on takeoffs? About lift decreasing the weight on the landing gear and all?

Pretty much, but it's also because of the motion I believe.

Essentially yes, although its more of a weather cocking effect than a comlete lateral push. You have to remeber almost all aircraft have a huge sail on the back (the fin). In larger aircraft this in some ways accentuates the effect. It is countered in exactly the same way though, using into wind aileron and judicious use of the rudder.

Ok, so crosswind can affect big aircraft on takeoffs. But is my "theory" correct? About how can quite weak wind of 10-15 knots push aircraft on takeoffs? About lift decreasing the weight on the landing gear and all?

Every aircraft, large and small, has its limits. The wind will indeed push the airplane even when there's plenty of weight-and attendant friction- on the wheels.

Today I saw a parked Breezy- which has no fuselage, only an open frame, start to slowly roll forward as the 5-10 knot breeze caught its drooping elevators and, I guess, the back of the rear seat. Nobody was aboard, but a Breezy is no ultralight...it weighs  over 1000 lbs. There was just enough downhill grade where it was parked so that the light wind could get it going.

But that's very different from what you're asking about...so I'll tell you what I've experienced flying real airplanes.

Most airplanes will "weathervane"- that is, try to put their nose into the wind- on the takeoff roll... some more, some less. They also will do it as you're landing. This is why "running out of rudder" in a crosswind takeoff or landing is more likely a problem than needing lots of aileron, even when the wheels are not really carrying any weight.

But rest assured that just as a plane will drift downwind, sideways to the runway, when it's become airborne, or when it's about to touch down, the wind can and will push it sideways while it's rolling... especially if the pilot is wisely putting in lots of rudder to keep the nose- and the tail, and the entire area of the fuselage- broadside to the wind to counteract weathervaning.

In fact, a lighter plane may "crow hop"- that is, sort of "trip over" the downwind wheel and hop sideways... and of course on a wet or icy runway, it may just slide downwind unless the pilot actually coordinates rudder and aileron to turn into the wind and crab as if the plane was airborne. I've really noticed this sort of thing while either landing or taking off, at that strange moment when you're not really rolling and not really flying....because yes, as the wings produce more lift, there is less weight- and thus friction- on the wheels.

Typically, though, the airplane controls can counteract this force nicely as long as the wind is "within limits". The maximum crosswind component is where the manufacturer backs off and says" we don't know if it will stay on the runway in wind stronger than that; you're on your own..."  ;D

Yeah..What Rotty said..

How do pilots deal with this, the same as with a Cessna 172, aileron in to the wind, in RL?

Not exactly. Typically only the rudder keeps directional control when on the ground. It prevents the fuselage from getting blown to a side (think of a weathervane). You actually just use aileron deflection into the wind to keep the wing from being lifted and to keep the weight of the aircraft on the gear. As you gain airspeed and lift, you also typically  start to reduce the amount of aileron deflection needed.

Heavier aircraft are not affected the same as a light general aviation aircraft is. The heavier the plane is, the stronger the wind needs to be to affect it in the same way.

Someone mentioned "crow hopping". If a plane gets to that point, then either the conditions are above the skills of the pilot and/ or the performance of the plane. A crow hop also puts serious stress on the gear and can cause serious damage over time.