Advanced Helicopter Flight Principles 1955 US Army Training Film TF46-2211

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Advanced Helicopter Flight Principles Part II, US Army training film TF46-2211

Public domain film from the US National Archives, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).

There is a broadband hum in the vocal frequencies of this film which I cannot completely remove.

from the FAA "Basic Helicopter Handbook"
http://avstop.com/ac/basichelicopterhandbook/ch4.html

Chapter 4. FUNCTION OF THE CONTROLS

There are four controls in the helicopter that the pilot must use during flight. They are (1) collective pitch control; (2) throttle control; (3) antitorque pedals (auxiliary or tail rotor control); and (4) cyclic pitch control.

Collective pitch control

The collective pitch lever or stick is located by the left side of the pilot's seat and is operated with the left hand. This lever moves up and down pivoting about the aft end and, through a series of mechanical linkages, changes the pitch angle of the main rotor blades. As the collective pitch lever is raised, there is a simultaneous and equal increase in the pitch angle of all the main rotor blades; as the lever is lowered, there is a simultaneous and equal decrease in the pitch angle. The amount of movement of the lever determines the amount of blade pitch change.

As the pitch angle of the rotor blades is changed, the angle of attack of each blade will also be changed. A change in the angle of attack changes the drag on the rotor blades. As the angle of attack increase, drag increases and rotor RPM and engine RPM (the needles are joined) tend to decrease; as the angle of attack decreases, drag decreases and the RPM tends to increase. Since it is essential that the RPM remain constant, there must be some means of making a proportionate change in power to compensate for the change in drag. This coordination of power change with blade pitch angle change is controlled through a collective pitch lever-throttle control cam linkage which automatically increases power when the collective pitch lever is raised, and decreases power when the lever is lowered.

The collective pitch control is the primary altitude control. Raising the collective pitch lever increases the rotor's lift and, through the cam linkage with the throttle, increases engine power....

Throttle control

The throttle is mounted on the forward end of the collective pitch lever in the form of a motor-cycle-type twist grip. The function of the throttle is to regulate RPM. If the collective pitch-throttle synchronization unit does not automatically maintain a constant RPM when a change is made in the collective pitch stick position, the throttle may be moved manually with the twist grip to make further adjustments of engine RPM. Twisting the throttle outboard increases RPM; twisting it inboard decreases RPM.

The throttle must be coordinated with the collective pitch so that a correct rotor RPM is maintained. The throttle, therefore, is the primary RPM control.

Collective pitch-throttle coordination

Collective pitch is the primary control for manifold pressure; the throttle is the primary control for RPM. Since the collective pitch control also influences RPM, and the throttle also influences manifold pressure, each is considered to be a secondary control of the other's functions. Therefore, the pilot must analyze both the tachometer (RPM indicator) and manifold pressure gauge to determine which control to use and how much. To best illustrate the relationship, a few problems with solutions follow:

Problem: RPM low, manifold pressure low.

Solution: Increasing the throttle will increase the RPM and the manifold pressure.

Problem: RPM low, manifold pressure high.

Solution: Lowering the collective pitch will reduce the manifold pressure, decrease drag on the rotor, and therefore, increase the RPM.

Problem: RPM high, manifold pressure high.

Solution: Decreasing the throttle reduces the RPM and the manifold pressure.

Problem: RPM high, manifold pressure low.

Solution: Raising the collective pitch will increase the manifold pressure, increase drag on the rotor, and therefore, decrease the RPM...

As with any other aircraft controls, large adjustments of either collective pitch or throttle should be avoided. All corrections should be accomplished through the use of smooth pressures.

Antitorque pedals

The thrust produced by the auxiliary (tail) rotor is governed by the position of the antitorque pedals...

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