Take Offs Part 2

//Take Offs Part 2

Take Offs Part 2

Now we are ready to talk about flying the Stearman. Once you have completed your run-up and are ready for take-off, be sure to check the area for inbound traffic and position your seat height as you desire. When you are in position on the runway make a final wind check and mentally prepare yourself for the take-off. Roll forward a few feet to align the tailwheel and if you have a Stearman with the free swivel tailwheel, lock it at this time.

The WW II U.S. Navy Flight Training Manual and the training films, as well as almost every book about flying tailwheel airplanes that I have ever read, recommend that the control stick be held slightly aft of neutral, thus providing some up elevator. This stick position will allow the airflow from the prop blast and headwind to help keep the tail down and provide positive directional control steering during the initial portion of the take-off roll. However, I prefer to have a full aft control stick position and full up elevator to achieve this goal. I was taught to fly tailwheel airplanes that way and that is the method I teach to my students.

As you initiate the take-off roll it is important that the pilot’s body, and his head in particular, be aligned with the centerline of the fuselage along the longitudinal axis of the airplane. The common tendency of many Stearman pilots is to lean to one side or the other of the cockpit in order to look around the side of the windshield and alongside the fuselage past the engine in order to gain better visibility. Usually, pilots lean to the left side as this is most natural since the left hand is on the throttle on the left side of the cockpit and the right hand is on the control stick. The consequence of this leaning can be that the control stick is drawn to the left side of the airplane introducing up aileron on that side. That results in the left wings being forced down whether that’s where you want them or not. So it is imperative that the pilot should remain aligned with the centerline of the airplane to avoid this unneeded control input.

The pilot should sit straight and with his peripheral vision look past the windshield between the wings and alongside the fuselage at an angle so as to focus on the edge of the runway several hundred feet in front of the airplane. In this manner he can judge the alignment of the airplane with the runway and make the appropriate control corrections for any drift.

Also, if there are any types of landmarks some distance from the departure end of the runway, such as trees, buildings, towers or mountain peaks, etc., they can also be used to give a visual sight picture of the projected runway heading. This can help in maintaining the runway sight path. Once becoming airborne they also can assist the pilot in correcting his flight path along the projected runway heading in correlation to any crosswind which might be present.

Begin the take-off roll with the stick full back for full up elevator and aileron into the wind if a crosswind is present. (More on this later) The heels of your feet should be on the floorboards and off the brakes. The throttle should be advanced smoothly, but positively, to the full open position. However, if you are flying a Stearman powered by the Continental W-670, 220 h.p. engine, this might be problematic. If you advance the throttle abruptly the engine r.p.m. initially may fail to accelerate and it will snort, cough, bark, fart and hesitate momentarily before it eventually will catch and accelerate to full r.p.m. This phenomenon is what is commonly called “The Continental Cough.” It is a normal characteristic of the engine. There is not anything wrong with the engine if it does this, so don’t be overly concerned when this occurs. This stuttering engine occurrence can also be encountered when you advance the throttle for take-off while doing touch and go landings.

Well known radial engine overhaul specialist, Don Sanders of Sanders Airmotive, Inc. in Mustang, Oklahoma, explained this condition to me in layman’s terms as follows. The Continental W-670 has a design feature that creates a “dead spot” in the engine where it doesn’t want to accelerate through smoothly, especially if the throttle is advanced rapidly. This “Continental Cough” usually occurs in the range of about 1000 r.p.m. to 1400 r.p.m. The W-670 was originally equipped with a Stromberg NA-R6D carburetor. During WW II Stromberg developed the NA-R6G in an effort to try to alleviate this problem somewhat. On November 25, 1942 Stromberg issued “Aircraft Carburetor Service Bulletin #59” which recommended that all NA-R6D carburetors be modified into a NA-R6G model. So if you happen to have a NA-R6D carburetor on your engine, you might want to consider having it modified to -6G standards or replacing it completely with a NA-R6G. The other engines that were installed in the original stock Stearmans are the Lycoming R-680 and the Jacobs R-755. Neither of these engines exhibit this problem.

A technique that I have used for many years to try to reduce this occurrence on take-off is that when I initially advance the throttle I move it forward only an inch or so. The engine r.p.m. will start to spool up a little. Once it begins spooling up a bit, I then advance the throttle smoothly to its full forward position. Try it. You’ll like it.

As the speed increases after the application of full power ease the control stick forward, raising the tail off the ground and attain a shallow climbing pitch attitude. Maintain this attitude throughout the take-off run. As the airplane approaches take-off airspeed gently apply back pressure to the stick and allow the Stearman to fly off the ground. Then assume a normal climb attitude.

Now, back to the point of the take-off when you are applying forward stick to add down elevator to raise the tail off the ground. The moment that the tail is lifted is the first critical point in the take-off roll. The torque due to P-Factor will decrease to zero since the Stearman is now approaching a level flight attitude. On the other hand, torque due to gyroscopic precession of the propeller will come into play during the act of raising the tail and then it will disappear. It will reach a level of intensity directly proportional to how quickly the tail is raised. So it is better if the pilot raises the tail slowly so the torque can be controlled better. As the take-off roll is started the pilot should anticipate the torque and apply right rudder as required to maintain a straight roll. He should also anticipate the need for additional right rudder as the tail is being raised. This is the most critical point in the take-off roll.

It is possible that the tail can be raised so quickly at a fairly low airspeed that the pilot will run out of available rudder with the result that the Stearman will veer off to the left even though right rudder is fully deflected.

Once the tail is in the air and the Stearman is rolling on the main wheels the directional control problems on the take-off are greatly reduced, but not completely absent. With the tail up the pilot’s visibility over the nose will increase and his ability to see the runway and judge his drift also will improve. As the airplane rolls down the runway make smooth rudder inputs to try to keep it going straight. Be sure that your feet are not up on the brakes. If that occurs and you start getting the brakes applied as you move the rudder you can expect some severe swerves from side to side and a very exciting ride.

I’m sure we all have observed Stearman take-offs where the airplane swerves from one side to the other with the rudder wig-wagging frantically and everyone’s hearts (including the pilot’s) are up in their throats hoping the Stearman will get airborne before it meets disaster somewhere off the side of the runway. Remember – once you make a rudder input on take-off to correct for a swerve you will have to almost immediately take that input OUT with opposite rudder to maintain control and a straight path. The fly off portion of the take-off is the easiest part of the event. Just a slight amount of up elevator pressure will increase the angle of attack of the wings and lift will accomplish the rest. Try not to yank back on the stick and launch the airplane into the air. Be smooth. As the tail is lowered somewhat for the lift off, some P-Factor will re-enter the equation. Generally speaking though, it will be inconsequential and can be easily compensated for by a slight amount of right rudder input.

Finally, the WW II U.S. Navy Flight Training Manual, as well as the Navy training films, both recommend that after the climb has been established in the Stearman powered by a Continental W-670, 220 h.p. engine, the throttle be retarded to a position of approximately ¾ of full throttle travel. I would guess that a good portion of today’s Stearman pilots do not do this and climb to level off altitude with the throttle still full forward. That is OK and has no ill-effects on the engine operation.

As mentioned earlier, the Continental W-670 engine is equipped with either the Stromberg NA-R6D or NA-R6G carburetor. These carburetors have two fuel jets. The main fuel jet is in operation at all times. The second one is called an economizer jet and is activated mechanically when the throttle is advanced past the approximate ¾ position towards the full throttle position. By retarding the throttle back to the approximate ¾ position you remove this economizer jet from operation. You will not notice any decrease in engine r.p.m., power or sound, but you may save a bit of fuel! The engines on the other stock Stearmans, the Lycoming R-680 and the Jacobs R-755 both are equipped with the Stromberg NAR7 carburetor. It also has an economizer jet and you could benefit with some fuel savings by reducing the throttle position back in climb with these engines also.

All the items discussed in the previous section of this article continue to be factors in a crosswind take-off. The additional basic compensations during a crosswind take-off really are as simple as they are necessary. These steps are:

  1. Keep the upwind wings down with aileron deflection into the wind to prevent the wind from getting underneath and lifting them. This will require the use of opposite rudder to keep the Stearman tracking straight.
  2. Keep the airplane tracking straight on the take-off roll with rudder. Additional rudder will be required to compensate for the weathervaning tendency caused by the crosswind.
  3. Raise the tail slightly higher than for a normal take-off so the Stearman can accelerate to a higher airspeed than normal before lift off.
  4. Once the Stearman is airborne, relax the rudder pressure to allow the airplane to crab into the wind and level the wings.

With the Stearman in a wings level attitude the upwind wings will normally have greater lift than the downwind wings. The downwind lower wing also will be affected by the fuselage. This, in itself, may not be all that significant. But any difference in the amount of lift created by each set of wings will result in an undesirable bank away from the wind unless action is taken to prevent it. It is better to take corrective action in anticipation of the wind effects, rather than after the fact.

The cure for all this is to apply up aileron into the wind. That will reduce the lift on the upwind wings and also when the airspeed increases the airflow striking the deflected ailerons will help lower the upwind wings. In addition, the slightly greater amount of aerodynamic drag created by the down aileron on the downwind side can also help counteract the weathervaning tendency somewhat and aid in maintaining a straight path on the take-off roll. The correct procedure is to apply full aileron into the wind before the take-off roll is started and to gradually reduce the aileron deflection as the airspeed increases. The goal is to maintain the wings in a level attitude throughout the take-off roll. Remember that banking an airplane generally results in a turn due to the tilted lift vector. A turn at this point is exactly what you do not want. You want to keep the wings level and the Stearman headed straight down the runway. Thus, you must also apply opposite rudder which will result in a straight path, but with the controls crossed.

The pilot also wants to ensure that the airplane leaves the ground only once without coming back down to bounce on the ground. In the case with a crosswind, a descent back onto the ground after lift off will also include a drift component. That is not good, especially in a Stearman. This can be prevented by raising the tail slightly higher than normal and allowing the airspeed to build to a higher value than what would be expected in a normal take-off. This slightly higher airspeed will ensure that the Stearman remains airborne once it leaves the ground.

Throughout the take-off roll in a crosswind the control pressures will vary as the airspeed increases. At the beginning of the take-off roll, the aileron control should be full over into the wind. However, as the airspeed increases the control input should be gradually reduced as required to keep the wings level. While all this is going on the Stearman should be kept tracking straight down the runway by whatever rudder input is required, usually opposite rudder.

A majority of crosswind take-offs that go sour probably begin with the pilot’s ignorance or disregard of the wind conditions. He may start the take-off roll without attempting to lower the upwind wings either because he forgot this crucial step or he postponed any input until the airspeed had increased some. In either case, this is an error.

For an example let’s assume that we have a right crosswind. Without any aileron compensation the right wings will be lifted slightly and the airplane will have a tendency to turn left due to the slight bank angle as well as from all the torque effects. Soon the right wings will have enough lift to fly while the left wings will not. The right wheel will come off the ground with the Stearman turning left and heading towards the weeds. The pilot, now scared out of his wits, may be lucky enough to yank it off the ground on the verge of a stall or he may end up skipping across the runway which could generate a vicious ground loop to the right. I’d bet we all have seen or heard about this happening to a hapless Stearman pilot.

In a slightly different version of this scenario, the right wings will lift and raise the right wheel off the ground. The right crosswind will strike the rudder and vertical stabilizer and cause the Stearman to weathervane and turn to the right. This combination, along with the addition of centrifugal force, will cause the lower left wingtip to drag during the ensuing ground loop. Not good! All of this could have been avoided by the proper use of crosswind techniques.

Over the years I have observed that many Stearman pilots have difficulties in making a proper crosswind take-off. Generally speaking, it involved either too much or too little aileron input coupled with sloppy rudder work. Quite often I’ve seen pilots put in full up aileron into the wind, but as the take-off progressed, they never took it out. This caused the upwind wings to be forced down unnecessarily during the take-off and when the Stearman lifted off it immediately started a roll into the wind. In some cases they even would continue to hold aileron and opposite rudder and climb out in a wings down attitude rather than with the wings level. This shows a basic lack of feel for flying the airplane and certainly is uncomfortable for any passenger. Besides that, it is a display of poor airmanship.

On the other hand, the other example described earlier has also been observed many times where inadequate aileron has been applied and the upwind wings rise and create a turn away from the crosswind. This is another example of poor airmanship which can lead to disaster.

In conclusion, remember that a properly executed crosswind take-off will require a longer take-off run than normal. This results from: a reduced headwind component; reduced effective lift due to a tilted lift vector (wing down); higher airspeed used due to having the tail higher which produces a lower angle of attack of the wings and additional drag due to crossed controls.

By |2016-11-13T09:33:06+00:00November 19th, 2015|Flying-Wire|Comments Off on Take Offs Part 2

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