Taming The Beast: How To Fly the Curtiss Jenny

By Ken Glaze (18 June 2005)

Anyway, the two obvious items from the pilot's standpoint that makes the Jenny different than any other production aircraft in FS2004 are 1. it has no airspeed indicator gauge and 2. it has no elevator trim. However, the Jenny does have a way of telling the pilot what airspeed it's flying at and that is related to the lack of elevator trim. To show you how and why this is, I will now refer to my copy of the book Stick And Rudder, which states that:

Attitude controls airspeed.

To explain this simply: the amount of lift a wing creates is determined by airspeed and angle of attack. The higher the angle of attack (to a certain limit known as the stall) and/or the higher the airspeed (to another certain limit known as the inflight break-up), the higher the lift. Therefore, during straight, un-accelerated (not curving) flight, a given airspeed will have a corresponding angle of attack that allows the plane to fly at that airspeed, and any change in that angle (and/or airspeed) results in a change in flight path.

The way for us pilots to use this information is to focus on what we can directly control, which is the angle of attack using the elevator. This is called "attitude flying" and is a technique in which we use angle of attack (aka attitude) to control airspeed and throttle to control the rate of altitude change, either up or down. The application of this you see this every time a plane takes off: the attitude of the plane is increased until it lifts off the ground (or in the case of the Jenny and other tail draggers, takeoff airspeed is) and the plane climbs at a low airspeed. Once at altitude, if you reduce only power, the plane stops climbing and remains at the same airspeed. If you reduce only the attitude, the plane stops climbing and speeds up. This is attitude flying at work, high attitude equals slow airspeed and vice versa.

Now, remember than attitude is controlled by the elevator. Since the Jenny has no elevator trim, the amount of back pressure needed to deflect the elevator cannot be changed, so the position of the control stick always corresponds to the deflection of the elevators. Now for an exercise in basic logic: IF the attitude controls airspeed, AND the elevator controls attitude, AND the control stick always shows the position of the elevator, THEN the control stick's position indicates the current airspeed (or at least when the airspeed is changing to). This makes the Jenny an airplane that you really feel the airspeed: the harder you're pulling back the elevator, the slower the Jenny is flying.

Did you follow that? Well, for you visual learners, take a look as the first picture here. This is a completely stock-standard FS2004 Jenny at an airspeed of 49 knots in straight and level flight. Note the amount of up elevator; given our new knowledge of attitude flying, we know that this is a visual indication that the plane is flying slowly. Since the elevator has no trim, the control stick has to be held back to keep the elevator at this position, so the stick's position is back towards me in the cockpit and telling me we're flying slowly.

Now, in the second picture below, I've added full power and allowed the Jenny to stabilize. The airspeed is now 63 knots and the plane is in straight and level flight. There still is a little bit of up elevator, but not nearly as much as earlier, which means the stick is farther forward than in the first picture, which indicates we're going faster. If I were to pull the stick back to the position seen in the first picture, the aircraft would eventually return to 49 knots, but it would now it would be in a climb because of the increased power from the engine.

That's the real secret to flying the Jenny and the key to attitude flying, remembering that the throttle controls climb and the elevators control airspeed. This knowledge won't change your technique during cruise flight because airspeed isn't critical, but during final approach, this becomes very important because the stick position will be your primary indicator (and controller) of airspeed. If you find yourself too fast, pull back the stick slightly and leave it there. If you need to descend, reduce power. If you get too slow, release some back pressure and if you start descending too fast, add power. At first, you'll do these adjustments separately, but with a little practice, the adjustments will become second nature and happen at the same time. In the Jenny, the key is to memorize the amount of up elevator that gives you about 45-50 knots, then keep the elevator there throughout your approach and use the throttle to control your descent.

Now you know how to take advantage of what you probably first thought was a problem with the Jenny. In fact, this is one of the main reasons why this plane doesn't have an elevator trim in the first place; early pilots were expected to feel their airspeed, not read it from a gauge. Historically, pilots were also taught to judge airspeed by listening to the tone the air made as it went through the flying wires, which is something that FS2004 does with mixed success.

Now, refer back to the second picture and remember that the stock Jenny requires a small amount of up elevator even at full throttle to maintain straight and level flight. I don't know about you, but flying an airplane that always needs back pressure on the stick to keep it level is a bit irritating. The fix for this is simple, given our new knowledge of attitude flying and the ability to recognize the terms "horizontal tail" and "angle of incidence" inside the Aircraft.cfg file (this assumes you're comfortable editing this file). For those of you who are brave enough to play "virtual aircraft mechanic", I've found that setting the horizontal tail angle of incidence to negative one (-1.0) gives the Jenny a comfortable hands-off cruise of about 49 knots at 1175 RPM. In terms of the real aircraft, this changes the angle that the horizontal tail is mounted on the fuselage by lowering the leading edge by one degree. This increases the downward "lift" of the tail when the elevator is in the neutral position, which has the same effect as holding up elevator.

So, have I beat this subject into the ground, yet? Well, hopefully you now understand how attitude controls airspeed and how the lack of elevator trim makes the Jenny's control stick into its airspeed indicator. Most of you have probably spent a lot of time learning to fly using instruments, now here is a challenge that's completely the opposite of that, visual flying in its simplest form. Your altitude is how big the trees are, your airspeed is how the plane feels and your GPS is your knowledge of the area. So now go and dust off that old Curtiss Jenny and enjoy fixed-wing flying at it simplest (and don't use Control-Z to cheat on the airspeed)!

Footnote: Yes, this is a bibliography! Stick And Rudder, written in 1944 by Wolfgang Langewiesche, is the bible of attitude flying and is currently published by McGraw Hill. I also used Aerodynamics For Naval Aviators, written by H. H. Hurt in 1960. It originally was a Navy flight school textbook and is currently published by Aviation Supplies and Academy, Inc. Both are available online from various sources.

Ken Glaze
kglaze@san.rr.com