What do these aircraft controls do?

Factual Questions
1

A few days ago I took a short flight in a float plane, which I understand was a DHC-3 otter. I was sitting up front and had a chance to watch the pilot for most of the flight, but I was unable to identify a few of his controls and uncomfortable bugging him with questions that he probably heard multiple times every day. This page has a photo of the cockpit, and I was wondering if anybody could enlighten me as to the purpose of the three levers sitting directly above the control stick? I’m assuming the far left one was the throttle, but I’ll be darned if I know what the middle or right ones are for.

He also kept reaching above his head to fiddle with some kind of dial, but I couldn’t find a decent photo of that particular object.

2

I’m not sure about the exact set of controls on that plane, but commonly near the throttle there will be levers that controls the “mixture”, which is how rich or lean the ratio of fuel to air, and “pitch”, which is the angle at which the propeller blades chop through the air.

3

IANAPilot, but if I were a bettin’ man, I’d say that one of the other two was fuel mixture. Don’t know what the third one would be.

The dial over his head was probably trim, which you adjust so as to keep level flight after making a throttle adjustment.

S^G

4

From left: throttle, propeller pitch, and mixture.

5

You must have been in a radial engine otter. Sweet. A lot of these are getting converted to turbines and they’re ugly as hell.

6

I see… thank you, everyone, for your feedback! I never would’ve guessed that the fiddly dial would’ve probably been trim- I was under the mistaken impression that the rudders and control stick were the pilot’s only way of interacting with the control surfaces.

I had no idea about the mixer, but my guess for the lever that controls propeller pitch had been that it was some kind of adjustment necessitated by airspeed: I believe it was down all the way to the bottom for most of the flight, and the only time I can remember the pilot using it was as we descended: right as we began to decrease in altitude he pushed it all the way up and hit it a few times. My only guess at the time was that it deployed the landing gear, and that guess sounded reasonable for the five or so seconds that it took for me to realize that it was equipped with pontoons. :smack:

7

The “pitch” control is actually an RPM control, it doesn’t control pitch directly, rather you set a desired propeller RPM and the propeller makes constant automatic pitch adjustments to maintain the set RPM regardless of airspeed. In more simple aircraft that don’t have a propeller control the propeller pitch is fixed and the RPMs will vary with changes in airspeed. Aircraft with fixed pitch props are at risk of an engine over-speed in certain flight regimes and the blade angle is a compromise between high speed and low speed performance. The aircraft with adjustable RPM (constant speed unit) have better a better range of performance because the blade angle is always adjusting to meet the current demands on it.

All the trim does is change the “hands free” position of the flight controls so that you’re not always having to apply pressure to the control column. to keep the aeroplane pointed where you want it. Almost all aircraft can be trimmed in pitch (nose up/down) and this requires changes whenever power settings and airspeed changes. Most have a rudder trim and this should also be adjusted with airspeed and power changes, though some aircraft are much more sensitive to speed and power changes than others. Adjustable aileron trim is less common and is generally a set and forget control (the aileron trim may never be touched in a particular aeroplane for months.)

In general power levers/throttles are black, RPM controls are either black or blue, and the mixture is red.

Some float planes with pontoons still have retractable wheels for landing on a runway.

8

More than anyone wants to know about floatplanes.

You may have been closer than you realize. The land-based Otter has fixed landing gear. (On the landing checklist, pilots sometimes say “down and welded”; we’re such cutups.) But some “pontoons” (in the biz, they’re called floats) can operate on land or water (called “amphibious”, or just “amphib”) and the wheels on those are retractable. Wheels down for land, up for water, and do not get them mixed up.

Floats also have water rudders that extend and retract. (See this page, scroll down to the diagram and the picture.) Water rudders are down for low-speed maneuvering on water, and up at all other times for less drag and less chance of damaging them.

Where I worked, we put the water rudder control on the floor between the two front seats; raising, lowering and steering was by cables. Raising and lowering the wheels was by hydraulics, with the control on the floor or on the panel. There’s no easy way to run a steering linkage to the wheels, so slow-speed steering on the ground was done by braking one side or the other.

If anyone has ever driven a car with one tire going down, you know what it feels like to hold the wheel in place when it wants to turn. Planes are like that, but moreso. When you’re climbing away from an airport, it’s a lot easier to crank in some nose-up trim than to pull the yoke back and hold it for a few minutes.

But, I had one flying lesson that I’ll never forget. We had the plane trimmed to fly straight-and-level at 80 mph, with the hands off the controls. My instructor had me pull the throttle back. Instead of slowing down, the plane started to descend, still going 80 mph. Push the throttle in, and we leveled off. Push it in a little more, and we started to climb; all while going at 80 mph and not touching anything else.

The interaction of power, yoke, and trim is a litttle more complicated than it seems at first.