Post by Tom Goodrick on Apr 16, 2012 16:47:04 GMT -5
Last night I awoke after dreaming I needed a new high altitude aircraft to carry out some important operation. (Not sure what that was.) Just before awakening, I thought of an answer: I needed a Beech A36TC. I knew how to make one but first I had to do some research. I vaguely remembered that the A36TC had gone through some changes in its early years. So this morning the first thing I did was to take an 300hp A36 and put a turbocharged engine on it. I have an A36 that came from a collection of AI aircraft in 2005 by Klaus Brosemann with a series of fancy paint jobs by John Bridgham. There are about 36 different paint jobs.
Brosemann's A36 looks very nice with one small error. He left the bottom of the fuselage rounded where it should be perfectly flat from the cabin to the tail cone. That is how they were made, just like the V35 Bonaza and the Baron Series of twins. Walter Beech liked flat bottoms because they reduced drag by spoiling the flow along the back side of the fuselage. But I admit, round bottoms look better. So these nice-looking aircraft are waiting to be flown in either the normal or the turbocharged versions.
My research also turned up the fact that in 1983 the A36TC became the B36TC with a longer wingspan to reduce drag at moderate angles of attack. They increased the gross weight by nearly 400 lbs and almost doubled the fuel capacity. This gives the new B36TC single a range of about 1000 nm with reserves (with a reduced payload).
So it did not take much work to get it flying. I just set the engine for auto mixture control and a critical altitude of 22000 ft and used the throttle to limit over-boosting on takeoff and climb using a power meter for the 300 hp engine. A little drag adjustment in cruise at 25,000 ft set 194 KTAS at 75% power. That is right on spec. The original FD was good for the normal engine so that 75% power gives the proper fuel flow of 15.7 gph. (Flow is directly proportional to power, regardless of the circumstances under which you get the power.)
One of the best things about the A36 Bonanza was that it fixed the CG creep problem of the original Bonanza. It was just a matter of mounting the wing correctly. (Walter Beech would be thoughly teed off to hear that assessment.) But the original bonaza had the problem where if you load it up front to back just meeting the CG position and gross weight, then while you are flying happily along toward your destination, the CG is moving aft until it can be out of the aft limit when you fly final at your destination. With the extra seats and baggage area in the A36 that could have made a significant problem. But the fixed it and in my FD models of the Bonanza I have accurately modeled this aspect. Be careful with the V35B and don't worry with the A36. Just loaded them each correctly (CG at about 30% or less).
If you fly this B36TG, you will find the secret of turbocharging. It simply lets the engine carry a high percentage of its max continuous power into the high altitude. It cruises in the range of 150-160 KIAS depending on power level just as it would at low altitude. But being at high altitude gives it a true airspeed 40 to nearly 50 knots faster than it would otherwise fly. The turbocharger compresses the air fed to the engine so it seems like air at low altitude.
On takeoff you advance the throttle to the 75% position (if someone gives you a throttle position indicator or scale and then work it up until you see 100% power for the finish of the takeoff and into the climb. Then you climb at about 1000 fpm all the way to your cruise altitude. (At high weights when climbing above 18000 ft you need to use 800 fpm). Cruise speed is close to or a little under 200 knots with a fuel flow just under 16 gph. That will get you there over the tallest mountain ranges in the US while the big wing lets you down gently on a short runway at a small airport.
But there is a slight problem with turbocharged aircraft without pressurization. You must descend rather slowly compared to aircraft with pressurized cabins. 500 fpm is the typical descent rate most passengers can tolerate. This gives you, the pilot, a significant challenge. Gain as much benefit as possible from the high-altitude cruise then get down properly for the approach at the destination.
Send me an email and I'll send an FD file if you already have the plain A36 or a complete package if you need it.
I am glad I didn't let my wife dump all those old aviation magazines - yet.
Brosemann's A36 looks very nice with one small error. He left the bottom of the fuselage rounded where it should be perfectly flat from the cabin to the tail cone. That is how they were made, just like the V35 Bonaza and the Baron Series of twins. Walter Beech liked flat bottoms because they reduced drag by spoiling the flow along the back side of the fuselage. But I admit, round bottoms look better. So these nice-looking aircraft are waiting to be flown in either the normal or the turbocharged versions.
My research also turned up the fact that in 1983 the A36TC became the B36TC with a longer wingspan to reduce drag at moderate angles of attack. They increased the gross weight by nearly 400 lbs and almost doubled the fuel capacity. This gives the new B36TC single a range of about 1000 nm with reserves (with a reduced payload).
So it did not take much work to get it flying. I just set the engine for auto mixture control and a critical altitude of 22000 ft and used the throttle to limit over-boosting on takeoff and climb using a power meter for the 300 hp engine. A little drag adjustment in cruise at 25,000 ft set 194 KTAS at 75% power. That is right on spec. The original FD was good for the normal engine so that 75% power gives the proper fuel flow of 15.7 gph. (Flow is directly proportional to power, regardless of the circumstances under which you get the power.)
One of the best things about the A36 Bonanza was that it fixed the CG creep problem of the original Bonanza. It was just a matter of mounting the wing correctly. (Walter Beech would be thoughly teed off to hear that assessment.) But the original bonaza had the problem where if you load it up front to back just meeting the CG position and gross weight, then while you are flying happily along toward your destination, the CG is moving aft until it can be out of the aft limit when you fly final at your destination. With the extra seats and baggage area in the A36 that could have made a significant problem. But the fixed it and in my FD models of the Bonanza I have accurately modeled this aspect. Be careful with the V35B and don't worry with the A36. Just loaded them each correctly (CG at about 30% or less).
If you fly this B36TG, you will find the secret of turbocharging. It simply lets the engine carry a high percentage of its max continuous power into the high altitude. It cruises in the range of 150-160 KIAS depending on power level just as it would at low altitude. But being at high altitude gives it a true airspeed 40 to nearly 50 knots faster than it would otherwise fly. The turbocharger compresses the air fed to the engine so it seems like air at low altitude.
On takeoff you advance the throttle to the 75% position (if someone gives you a throttle position indicator or scale and then work it up until you see 100% power for the finish of the takeoff and into the climb. Then you climb at about 1000 fpm all the way to your cruise altitude. (At high weights when climbing above 18000 ft you need to use 800 fpm). Cruise speed is close to or a little under 200 knots with a fuel flow just under 16 gph. That will get you there over the tallest mountain ranges in the US while the big wing lets you down gently on a short runway at a small airport.
But there is a slight problem with turbocharged aircraft without pressurization. You must descend rather slowly compared to aircraft with pressurized cabins. 500 fpm is the typical descent rate most passengers can tolerate. This gives you, the pilot, a significant challenge. Gain as much benefit as possible from the high-altitude cruise then get down properly for the approach at the destination.
Send me an email and I'll send an FD file if you already have the plain A36 or a complete package if you need it.
I am glad I didn't let my wife dump all those old aviation magazines - yet.