BD-5 Information Memo - No. 11

First Pilot Test Report

By Les Berven, Chief Flight Test Pilot

It has been my privilege to be the very first test pilot to fly the all-metal version of the BD-5 Micro. In only a few short flights, this little airplane has impressed me so much that I would like to share with anyone who will listen, a pilot's view of the flight of this remarkable aircraft.

The airplane we have been flying at the Bede Flight Test Center is Newton is the long wing version with the 45 hp engine. This aircraft has a test nose boom to give us a predictable pitot-static system for the initial flight testing, extensive engine and temperature instrumentation, a tape recorder and an over-the-shoulder movie camera to record flight test data. With all its modifications and test instrumentation, this particular aircraft, N501BD, is considerably heavier than the production BD-5. Take-off weight of the last three flights has been 700 lbs. (The second flight down the runway at 90 mph at a height of 30 to 40 feet was made at 750 lbs. with a smaller 33 bhp engine!) The center of gravity for all the flights has been 26% MAC.

The preflight instruction is very short and simple:

  1. Cockpit
  2. Pitot cover removed
  3. Fuel, check quantity visually
  4. Control surfaces, check for freedom of movement
  5. Propeller, check for nicks, pull through and check engine
  6. Engine access door, secure
  7. Speed brake, cowl flap open
  8. Landing gear
  9. Flaps, check attachment and engine

The easiest way to get into the cockpit is from the left side. You put your right foot into the seat, hands on the canopy rails, left foot into the seat, hands down to the arm rests and support your weight on your arms. Slide your feet forward to the rudder pedals and sit down. At this point, the cockpit is so beautiful. It looks so much like an F-104 (supersonic interceptor of the 60's and 70's) that your heart rate goes up to about 120/minute, and your mouth starts to water uncontrollably.

The before-engine-start checklist goes like this:

  1. Seat-belt and shoulder harness fastened
  2. Headset plugged into the jack
  3. Control valve on
  4. Speedbrake and cowl flap closed
  5. Throttle idle
  6. Variable speed drive control, takeoff position (about 3/4 forward)
  7. Trim, takeoff position neutral for model 1BD
  8. Mixture full rich
  9. Instrument check, accelerometer reset, altimeter set, vertical speed zeroed and noted
  10. Landing gear handle, down
  11. Circuit breakers, in
  12. Flaps retracted
  13. Tail stands, retract
  14. Choke, push off
  15. Master switch off
  16. Ignition switch off
  17. Starter off
  18. Ammeter, zero
  19. Flight controls, check freedom of movement
  20. Canopy position optional

You are now ready to start the engine which is accomplished as follows:

  1. Engine start

Choke to 1/2 as soon as the engine fires and full in after the engine is running smoothly. Throttle at 2000 to 3000 for warm-up, radios on. I cannot tell a lie, at this point, the BD-5 does in fact sound like a small lawn mower. But only in idle. Once you bring the power up, the combination of prop noise and bumping engine has a unique sound all its own. I can't describe it because there's nothing like it. It just sounds like a BD-5.

Taxiing is great. There is no nose wheel steering but the full swivel nose wheel and excellent main gear brakes make it the most maneuverable aircraft on the ground I have ever taxied. With braking on one side, stopped condition, you can move the cockpit directly sideways. Rudder is effective at 20 mph IAS. For taxiing upwind you don't even need the brakes. The aircraft has a very low CG and feels very stable while taxiing.

I have made 180-degree turns at 15 mph within a turning radius of 35 feet. I felt very little tendency for the aircraft to tip over or to skid. Once you're moving, the BD-5 will taxi in a calm wind at idle power, 2000 rpm, at about 15 mph. The only undesirable taxi characteristic is a strong weathervane tendency because of the high directional stability. This requires maximum braking at 5000 rpm to turn downwind to 20 kt crosswind condition.

Pre-take-off checks are also very simple and consist of the following:

  1. Fuel, on
  2. Mixture, rich
  3. Trim, set
  4. Flaps, up
  5. Controls, check freedom of movement
  6. Variable speed drive, hold the brakes and run the engine up to full throttle, set the variable speed to attain 6500 rpm

With the fixed pitch cruise propeller, initial acceleration is only good. After 30 mph, it is phenomenal. Preflight differential braking is requires to an airspeed of 20 mph, then the rudder and ailerons become effective.

It is very easy to track straight down the runway, visibility is excellent. You can see ten feet in front of the nose. I normally hold full aft stick to lighten the load on the nose wheel. Power-on the nose wheel lifts off at 45 mph and comes off gently so there's no problem holding it right where you want it. You usually put the top of the instrument panel right on the horizon and hold it there until the aircraft flies off the runway at 75 mph IAS. This is not minimum lift off speed but gives a nice smooth takeoff. Stall speed with the flaps up at this weight, which is 100 lbs. over normal gross, is 62 mph CAS.

After lift off I continue to hold this same attitude, which is the top of the instrument panel on the horizon. Let the aircraft climb and accelerate to 100 mph IAS. At 100 mph I increase back pressure slightly to hold airspeed and continue to climb. At 85 degrees Fahrenheit, the pressure altitude at 1800 ft., the rate of climb is 500 to 600 ft/min. This is at 700 lbs. with the gear down and the speed brake cowl flap at 30 degrees. My rpm at this time is about 6700 with a takeoff variable speed drive setting. The cylinder head temperature stabilizes in climb at about 390 degrees F (redline is 450 degrees F). A little light and moderate turbulence makes the wing tips flex up and down about plus or minus 2 inches at 6 cycles per second (the primary bending frequency of the long wing). The aircraft is surprisingly good in turbulence -- it tracks straight ahead with no lateral directional oscillation at all. About the only noticeable turbulence in spots is the wing flexing, which gave an oscillating plus or minus 1/10 of a G. Almost no rudder force is required to climb straight ahead and there is essentially no P-factor during takeoff and rotation. The BD-5 accelerates and tracks directionally like a single-engine jet.

After exiting the pattern and climbing in an upward spiral I leveled off at 2500 ft AGL (4000 MSL). I leave the throttle full open and the variable speed drive set at the takeoff position. The aircraft will accelerate to 130 mph indicated (about 135 CAS) and the engine rpm will go to approximately 7000. (This is still gear down and speed brake cowl flaps open 30 degrees!). At a cruise rpm of 5500 the airspeed drops to 110 mph indicated where I trim any remaining longitudinal stick forces.

The trim rate and authority are perfect, not too sensitive but plenty of range. We won't change a thing there. The BD-5 is stable in all three axis, and the controls are the best harmonized of any aircraft I have ever flown. I once thought that nobody could beat the Beech T34 for control harmony, but the BD-5 is definitely better. Surprisingly, none of the controls is overly sensitive.

In this configuration, the longitudinal short period mode is dead beat in response to the stabilator mode. The directional short period has one overshoot with absolutely no tendency for the nose to wander in rough air, even with your feet off the pedals. Laterally, the BD-5 has a slight spiral divergence (which is normal), with surprisingly low adverse yaw. I had expected, with such a wide wingspan compared to the tail, that adverse yaw would be a problem. But not so! I could make a 30 degree bank turn with my feet off the rudder pedals and only slip on 1/2 ball during the roll-in.

Roll rate is excellent. In rolling from a 45 degree bank to the 45 degree left a full aileron deflection roll is faster than an American Yankee at 130 mph (which is darned fast). This is with the long wing at 110 mph! When I consider the short wing at 250 mph and full deflection aileron roll, my left leg twitches uncontrollably. Conservative calculations show it will roll more than twice as fast as a P-51.

Cockpit visibility is excellent. You can see aft 150 degrees on either side and you can look straight down since the pilot's eyes are just even with the leading edge of the wing. I have yet to see any distortion in the canopy at any angle.

Coming down is a problem. With the gear down and the speedbrake cowl at 30 degrees, idle power, the rate of descent at 100 mph is only 400 fpm. Not only that, but you have to beat yourself with a stick to decide to terminate a BD-5 flight. In only five flights I have a sprained face from grinning so much. The L over D with the gear and the speedbrake is so high that on the last three flights I shut the engine down on final so that I would come down faster. Engine out, the aircraft is still very stable and one of the easiest airplanes around to land. All you have to do is to fly down final at about 90 mph IAS (this will be slower but we haven't used the flaps yet), come on down to about one foot, and then flare at constant altitude until the top of the instrument panel is on the horizon and then just hold it there. The aircraft will continue to lose speed and will settle on its main gear so gently you'll hardly know you're down. Even better, there is no pitch down when the main gear touches. You can keep the pitch-up additive constant with very little effort down to 30 mph IAS, full aft stick. At this time, the nose generally comes down by itself and the nose wheel begins to roll. In a crosswind the crab on final slip to touchdown method works very well. The last landing I made was in a 17 kt wind 30 degrees from the left. I touch down on the left wheel and rolled for about 5 seconds and then let the right wing down. I held the nose off to 40 mph with no problem keeping the aircraft straight. Indeed, after only a few flights I can be quoted as saying that this aircraft is one of the easiest to land than any one of the currently popular training aircraft.

In fact, my overall impression of the BD-5 Micro is that it is a fighter plane that the student pilot can fly. Anyone with 10 hours solo time in a Yankee would have no problem with the BD-5. Me? I'm gonna buy two!

The BD-5 Development Program

By Burt Rutan, Director of Development

 The development of the BD-5 has been carried out in a unique environment and under ground rules that would be difficult to adhere to during development of a certified aircraft or military aircraft project. Our development team consists of one pilot, five design engineers, two test engineers and ten prototype workshop technicians. Our aircraft was designed primarily to certification requirements. None of the time- and dollar-consuming certification paperwork and procedures were required. The most recently certified light single-engine aircraft required 2.5 years and $9,000,000 to get it type-certified, and it is essentially the same as similar aircraft that have been flying for 25 years!

Because of this situation it is obvious that, under the present regulations, the only sure way the average person can hope to fly at a reasonable cost is to build his own aircraft. Unfortunately, this usually means that the average enthusiast ends up with an aircraft that has not been fully engineered or tested. Furthermore, the search for quality materials and hardware to complete a project becomes a tremendous task and often causes long delays before an individual's design reaches completion.

The BD-5 has been developed to overcome these problems, and has as its primary goals:

A large percentage of us at Bede Aircraft who have been working on the BD-5 are pilots ourselves, as well as having our own homebuilt aircraft projects. Because of this we have a deep understanding and appreciation for the needs of our BD-5 customers. With no controlling or regulatory restrictions from the outside, we have been afforded a large amount of flexibility. We have been able to make relatively major changes to the aircraft in a very short period of time, instead of having to "freeze" on the first design configuration that flew or operated successfully, thus allowing us to optimize all the BD-5's systems and flying qualities. This flexibility in the development program has been taken advantage of to allow a continuing progression towards the best design possible.

At first we were plagued with several small problems with our engine, control system and horizontal tail. These problem areas prevented us from making anything more than short flights down the runway. We did, however, eventually come up with fixes that completely resolved our problems. Some of the results of these is that the aircraft is now lighter, as well as easier to build.

When we did make our first flight out of the pattern, we found to our delight that not only did our problems vanish but an aircraft of quality and fine performance exceeded our most optimistic expectations. As of this writing we have flown at least once every day since the first out-of-the-pattern flight. When our test pilot, Les Berven, taxied in after the first flight, he turned to Jim Bede and said, "Think of how you would like it to handle, and it flies twice that good." We had hoped to have it docile enough for the 100-hour Yankee pilot, we now honestly feel that it is so easy to fly that even the low-time beginner will be delighted. Les feels the control on it is better than the T-34 Mentor, which has always been acclaimed as a pilot's airplane.

The engine control system and drive system are maintenance-free. The tooling we developed for these is better than the average certified light aircraft. In general, the time we spent on the ground perfecting the aircraft has rewarded us all with a truly magnificent airplane, one we are all sure will revolutionize sports and recreational aviation at low cost.

The New BD-5 Engine

After a lot of testing and negotiating, we have finally come to the conclusion we cannot use the Kiekhaefer Aeromarine engine in the BD-5.

After many frustrating months of placing production orders for the engine, only to have promised delivery dates pass, new purchase orders placed, substantial deposits given and then returned, and new purchase orders made, we have finally come to face the fact that there would be a tremendous delay in receiving production engines, if ever at all.

Testing has revealed a number of engine problems, all of which we felt could have been eventually solved. However, a lot of time and a lot of money has been lost in our efforts to use this engine. But then, from this frustrating experience we may have ended up with a blessing in disguise.

As we surveyed all alternate engine sources we found one that looked ideal and has already been approved for powered gliders in Europe. After we made our first flights down the runway in our all-metal BD-5 with the Kiekhafer engine, we obtained these new engines manufactured by Hirth of West Germany. After running them on a test dynamometer, we were so impressed we immediately installed one in the aircraft.

All our flights now have been made with the new Hirth engine. Results have been absolutely perfect. We have not had one single ounce of trouble. It starts, it runs, and it cools better than anything else we have ever seen. The weight, power and overall size are very similar to the engines we had originally planned to use. After a little further testing we will be able to give you specific specifications on all engine models available.

There is no question we are going to have to do some re-evaluating and re-testing before we can ship the production engines. It may take us as long as three more months before the final results are worked out, but we are certain the end result will be better than we originally had planned. We are receiving tremendous cooperation from the manufacturer of this engine, and they are cooperating with us in every way to modify or improve the engine to meet our most stringent requirements.

We have gone from a long frustrating experience into what is turning out to be an almost perfect aircraft engine. What others told us they could do, the Hirth engine is actually doing.

Last Update: 5/16/97
Web Author: Juan Jiménez
Copyright © 1997 by Juan Jiménez - ALL RIGHTS RESERVED