Tuesday, November 24, 2009

Flying the Turbo-normalized Bonanza

Flying the Turbo-normalized Bonanza
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If you have ever considered flying the Tornado Alley Turbo conversion on your Bonanza, I promise you an exciting ride. The Turbo-normalized version of your Bonanza is quite a different bird than it’s normally aspirated cousin. The Tornado Alley version is typically paired with Osborne tip tanks. The tips are necessary because the TN version drinks quite a bit of fuel. Normal fuel capacity in a BE-36 is 74 gallons useable. Osborne tips add an extra 20 gallons per side for a total of 114 gallons.

The Beechcraft machine that I am referring to is an A-36 Bonanza with the turbonormalizer conversion. This is not to be mistaken for a B-36 TC, which is a factory Bonanza with a turbo charger. The 36 TC has a longer wing and a different engine. The Tornado Alley is an STC mod that starts life as a plain vanilla A-36 Bonanza. The turbo-normalized version today is usually paired with the tip tanks, TKS anti-ice system and built-in oxygen. Basic empty weight will increase from approximately 2600 lbs to 2800 lbs. and the C.G. will move about 1 – 2 inches forward. The good news is that the STC allows an increase in gross weight from 3600 lbs to 4000 lbs. The only caveat is that above 3650 lbs, your Bonanza is no longer a utility category, it is now normal category. While operating in normal category, there are a few airspeed changes like reduced Va and approach flap speeds.

There is a phenomenon that we call the low altitude problem (LAP). Takeoff ground roll and climb are seriously degraded, up to 30%. I have noticed that the initial climb rate is somewhat anemic (300-500 fpm) up to 5000 feet density altitude. From that point on, it will climb nicely between 800 and 1000 fpm with 29.6 inches manifold pressure and 2500 rpm all the way to at least 15,000 ft. Fuel burn stays fairly constant through the climb @ 30-35 gph at an airpseed of 120 KIAS. Because of the increased ground roll, we suggest runway lengths of 3500 feet and more for safety. True airpseed @ 50 degrees F lean of peak at that altitude is about 170 knots. At that setting, fuel burn settles in about 15-16 gph.

This is a cross-country airplane. The increased fuel burn and decreased climb rate won’t pay for itself on an 80 -100 nm trip. You need to fly at least two or three hours to see the benefit. Of course, getting higher quicker is payment in itself. With the advantage of increased altitude and oxygen, you can fly above weather and take advantage of increased tailwinds and more comfortable flying.

The TKS de-icing/anti-icing system is available in it’s standard format or it’s known icing version. The only substantial difference between the two is an extra fluid pump (for the glycol solution) and a windshield strip to remove/prevent ice on the windshield. The TKS system, or weeping wing as it is sometimes called, works very well. It can be turned on prior to entering any icing condition (anti-ice mode) or turned on after ice has formed (de-ice mode). Typically, you will have enough fluid for one and one-half hours de-ice or 3 hours anti-ice. Prudence dictates that you should be out of the icing way before you need to shed ice for 3 hours!

Let’s break this down for simplicity sake:

• you put in a turbo-normalizer, tip tanks, TKS weeping wing, and built in oxygen
• your ground roll and low altitude performance decrease
• your initial climb decreases
• your empty weight increases by about 200 lbs
• your gross weight increases by 400 lbs
• now you benefit by an extra 200 lbs useful load
• you burn a lot more fuel in climb
• you can fly higher
• you can get to higher altitudes faster
• better true airspeeds
• you have great ice protection
• increased true airspeed as a result of higher manifold pressures at altitude

All is is available for approximately $100,000.00. For pilots that want/need to get above the weather, fly longer x-c trips, or fly higher in general, this system is wonderful. For the pilot looking to bore holes in the sky, you can probably pass on this option. I was told recently that TKS and Tornado Alley try to work together for you and get your Bonanza back to you in about six weeks turnaround time.

Paul Gretschel, BPPP
Coram, NY

1 comment:

  1. The power to weight ratio of the exhaust gas turbocharged

    engine is much better than that of the normal engine.
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