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# How Doesdoes the F-35B Not Flip Over During Transitionnot flip over during transition?

As the engine nozzle rotates, the lift-fan cannot. Wouldn't this imbalance of moments aroundaround the center of gravity result in the F-35 pitching up onto its back?

As can be seen at 5:14 in this video:

the F-35B is capable of transitioning from vertical hover to horizontal flight.

It accomplishes this in part by gradually rotating the engine nozzle from the vertical position to the horizontal.
Let us assume that the throttle input stays constant in the following scenario: As the nozzle rotates, the vertical component of its thrust is reduced (as the horizontal component increases) as

$$thrust_{horizontal} = thrust \cdot \cos(\theta)$$

$$\theta$$ being the angle between the jet exhaust and the vertical axis.
The problem is, the lift fan does not rotate. And since it is attached by shaft to the engine, we assume it always rotates at the same RPM as the engine itself.
Therefore, the vertical component of lift of the lift fan does not change for a given throttle input, while the vertical component of the jet engine nozzle does!

So as the nozzle transition occurs, the thrust of the lift fan (ahead of the center of gravity) stays constant, but the vertical thrust behind the center of gravity (rear engine nozzle) reduces: shouldn’t this cause the aircraft to pitch upwards and flip onto its back? Yet in the video the aircraft seems to pitch up only ten or so degrees (I assume due to the increased coefficient of lift on the wings) but otherwise stays flat in pitch.

The thrust of the lift fan must be somehow modulated to accomplish this, right? If so how is this done if its shaft speed is tied to that of the engine?

Possible solutions:
1. As the aircraft’s forward velocity increases, the lift of the wings compensates for the reduced vertical lift of the rear engine nozzle.
2. The aircraft pitches up so as to deflect the angle of the lift fan from the vertical to match the angle between the engine nozzle and vertical.

# How Does F-35B Not Flip Over During Transition?

As the engine nozzle rotates, the lift-fan cannot. Wouldn't this imbalance of moments around the center of gravity result in the F-35 pitching up onto its back?

As can be seen at 5:14 in this video:

the F-35B is capable of transitioning from vertical hover to horizontal flight.

It accomplishes this in part by gradually rotating the engine nozzle from the vertical position to the horizontal.
Let us assume that the throttle input stays constant in the following scenario: As the nozzle rotates, the vertical component of its thrust is reduced (as the horizontal component increases) as

$$thrust_{horizontal} = thrust \cdot \cos(\theta)$$

$$\theta$$ being the angle between the jet exhaust and the vertical axis.
The problem is, the lift fan does not rotate. And since it is attached by shaft to the engine, we assume it always rotates at the same RPM as the engine itself.
Therefore, the vertical component of lift of the lift fan does not change for a given throttle input, while the vertical component of the jet engine nozzle does!

So as the nozzle transition occurs, the thrust of the lift fan (ahead of the center of gravity) stays constant, but the vertical thrust behind the center of gravity (rear engine nozzle) reduces: shouldn’t this cause the aircraft to pitch upwards and flip onto its back? Yet in the video the aircraft seems to pitch up only ten or so degrees (I assume due to the increased coefficient of lift on the wings) but otherwise stays flat in pitch.

The thrust of the lift fan must be somehow modulated to accomplish this, right? If so how is this done if its shaft speed is tied to that of the engine?

Possible solutions:
1. As the aircraft’s forward velocity increases, the lift of the wings compensates for the reduced vertical lift of the rear engine nozzle.
2. The aircraft pitches up so as to deflect the angle of the lift fan from the vertical to match the angle between the engine nozzle and vertical.

# How does the F-35B not flip over during transition?

As the engine nozzle rotates, the lift-fan cannot. Wouldn't this imbalance of moments around the center of gravity result in the F-35 pitching up onto its back?

As can be seen at 5:14 in this video:

the F-35B is capable of transitioning from vertical hover to horizontal flight.

It accomplishes this in part by gradually rotating the engine nozzle from the vertical position to the horizontal.
Let us assume that the throttle input stays constant in the following scenario: As the nozzle rotates, the vertical component of its thrust is reduced (as the horizontal component increases) as

$$thrust_{horizontal} = thrust \cdot \cos(\theta)$$

$$\theta$$ being the angle between the jet exhaust and the vertical axis.
The problem is, the lift fan does not rotate. And since it is attached by shaft to the engine, we assume it always rotates at the same RPM as the engine itself.
Therefore, the vertical component of lift of the lift fan does not change for a given throttle input, while the vertical component of the jet engine nozzle does!

So as the nozzle transition occurs, the thrust of the lift fan (ahead of the center of gravity) stays constant, but the vertical thrust behind the center of gravity (rear engine nozzle) reduces: shouldn’t this cause the aircraft to pitch upwards and flip onto its back? Yet in the video the aircraft seems to pitch up only ten or so degrees (I assume due to the increased coefficient of lift on the wings) but otherwise stays flat in pitch.

The thrust of the lift fan must be somehow modulated to accomplish this, right? If so how is this done if its shaft speed is tied to that of the engine?

Possible solutions:
1. As the aircraft’s forward velocity increases, the lift of the wings compensates for the reduced vertical lift of the rear engine nozzle.
2. The aircraft pitches up so as to deflect the angle of the lift fan from the vertical to match the angle between the engine nozzle and vertical.

3 Question really needs the F35 tag over the thrust tag
2 added 14 characters in body

As the engine nozzle rotates, the lift-fan cannot. Wouldn't this imbalance of moments around the center of gravity result in the F-35 pitching up onto it'sits back?

As can be seen at 5:14 in this video:

, the F-35B is capable of transitioning from vertical hover to horizontal flight.

It accomplishes this in part by gradually rotating the engine nozzle from the vertical position to the horizontal.
Let us assume that the throttle input stays constant in the following scenario: As the nozzle rotates, the vertical component of its thrust is reduced (as the horizontal component increases) as

thrust horizontal = thrust * cos(Theta)$$thrust_{horizontal} = thrust \cdot \cos(\theta)$$

Theta$$\theta$$ being the angle between the jet exhaust and the vertical axis.
The problem is, the lift fan does not rotate. And since it is attached by shaft to the engine, we assume it always rotates at the same RPM as the engine itself.
Therefore, the vertical component of lift of the lift fan does not change for a given throttle input, while the vertical component of the jet engine nozzle does!

So as the nozzle transition occurs, the thrust of the lift fan (ahead of the center of gravity) stays constant, but the vertical thrust behind the center of gravity (rear engine nozzle) reduces: shouldn’t this cause the aircraft to pitch upwards and flip onto it’sits back? Yet in the video the aircraft seems to pitch up only ten or so degrees (assumingly forI assume due to the increased coefficient of lift on the wings) but otherwise stays flat in pitch.

The thrust of the lift fan must be somehow modulatemodulated to accomplish this yes, right? If so how is this done if its shaft speed is tied to that of the engine?

Possible solutions:
1). As the aircraft’s forward velocity increases, the lift of the wings compensates for the reduced vertical lift of the rear engine nozzle.
2). The aircraft pitches up so as to deflect the angle of the lift fan from the vertical to match the angle between the engine nozzle and vertical.

As the engine nozzle rotates, the lift-fan cannot. Wouldn't this imbalance of moments around the center of gravity result in the F-35 pitching up onto it's back?

As can be seen at 5:14 in this video:

, the F-35B is capable of transitioning from vertical hover to horizontal flight.

It accomplishes this in part by gradually rotating the engine nozzle from the vertical position to the horizontal. Let us assume that the throttle input stays constant in the following scenario: As the nozzle rotates, the vertical component of its thrust is reduced (as the horizontal component increases) as

thrust horizontal = thrust * cos(Theta)

Theta being the angle between the jet exhaust and the vertical axis.
The problem is, the lift fan does not rotate. And since it is attached by shaft to the engine, we assume it always rotates at the same RPM as the engine itself.
Therefore, the vertical component of lift of the lift fan does not change for a given throttle input, while the vertical component of the jet engine nozzle does!

So as the nozzle transition occurs, the thrust of the lift fan (ahead of center of gravity) stays constant, but the vertical thrust behind center of gravity (rear engine nozzle) reduces: shouldn’t this cause the aircraft to pitch upwards and flip onto it’s back? Yet in the video the aircraft seems to pitch up only ten or so degrees (assumingly for increased coefficient of lift on the wings) but otherwise stays flat in pitch.

The thrust of the lift fan must be somehow modulate to accomplish this yes? If so how is this done if its shaft speed is tied to that of the engine?

Possible solutions: 1) As the aircraft’s forward velocity increases, the lift of the wings compensates for the reduced vertical lift of the rear engine nozzle. 2) The aircraft pitches up so as to deflect the angle of the lift fan from the vertical to match the angle between the engine nozzle and vertical.

As the engine nozzle rotates, the lift-fan cannot. Wouldn't this imbalance of moments around the center of gravity result in the F-35 pitching up onto its back?

As can be seen at 5:14 in this video:

the F-35B is capable of transitioning from vertical hover to horizontal flight.

It accomplishes this in part by gradually rotating the engine nozzle from the vertical position to the horizontal.
Let us assume that the throttle input stays constant in the following scenario: As the nozzle rotates, the vertical component of its thrust is reduced (as the horizontal component increases) as

$$thrust_{horizontal} = thrust \cdot \cos(\theta)$$

$$\theta$$ being the angle between the jet exhaust and the vertical axis.
The problem is, the lift fan does not rotate. And since it is attached by shaft to the engine, we assume it always rotates at the same RPM as the engine itself.
Therefore, the vertical component of lift of the lift fan does not change for a given throttle input, while the vertical component of the jet engine nozzle does!

So as the nozzle transition occurs, the thrust of the lift fan (ahead of the center of gravity) stays constant, but the vertical thrust behind the center of gravity (rear engine nozzle) reduces: shouldn’t this cause the aircraft to pitch upwards and flip onto its back? Yet in the video the aircraft seems to pitch up only ten or so degrees (I assume due to the increased coefficient of lift on the wings) but otherwise stays flat in pitch.

The thrust of the lift fan must be somehow modulated to accomplish this, right? If so how is this done if its shaft speed is tied to that of the engine?

Possible solutions:
1. As the aircraft’s forward velocity increases, the lift of the wings compensates for the reduced vertical lift of the rear engine nozzle.
2. The aircraft pitches up so as to deflect the angle of the lift fan from the vertical to match the angle between the engine nozzle and vertical.

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