What Is "trail Position" For Cowl Gills?

[dswo 0]

The take-off checklist says to open the cowl gills to "trail position." How does one do that?

[Snave 466]

The switches are not `on` and `off` they are power-on and power-off to the gill motors. Stepping them on for only a brief period causes the gills to only open a little. Leaving them on causes the gills to open to fully- then returning the switch to the central position switches off the drive motors.

As the animation lags the switch (a bee-oo-tiful little touch actually!) it's only a couple minutes practice to flick the switch briefly, then pan round and up to see the results...

[Finn 873]

In Trail position the actuators for the cowflaps are unpowered.

That causes the cowflaps to flap freely in the windstream.This can´t be done in FSX though.

I would say that Trail position would be somewhere between 5-20% open, dependent on airspeed (the faster the less).

Finn

[Snave 466]

Yes, it's the same for the DC-3, and for similar reasons even though the DC-3 used hydraulic operation, and the Cat electric: The powered operation causes the motors to run (in the case of the DC-3 the valves to open), so all the time the actuators are in operation, they are powered. This presents a potential fire risk in the Cat, a potential to lose all hydraulics through a faulty valve in the DC-3.

The centre switch position actually represents a `neither on nor off` mode for the electric motors, leaving them free to flap, if they were not constrained by the airflow, but this is not represented in the sim.

In early Cats the electric motors for the cowling flaps were notoriously unreliable and often failed, leading to the FE having to hand-crank them. You can't hand crank against a screw-driven actuator assembly if its engaged.