and away - aero resources, inc
TRANSCRIPT
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Up, up, and awayTurbonormalizing improves an airplane's utility
BY STEVEN W. ELLS
YOU can take this one to the bankinstalling a turbonormalizer will improvean airplane's utility. This was demonstrated
following the installation of a Tornado AlleyTurbo (TAT) Whirlwind II turbonormalizersystem on the Superior Air Parts Certified Millennium engine in the AOPASweepstakes Bonanza.
Turbonormalizing the sweepstakesBonanza had the same effect on our
1966 Beech V35 Bonanza that Viagra
PHOTOGRAPH BY MIKE FIZER
apparently has had on Bob Dole-thesweepstakes Bonanza can now keep upwith airplanes half its age. Before wedescribe what was done, let's talk aboutwhy it was done.
Turbonormalizing will allow the winner of the sweepstakes Bonanza to morefully utilize the airplane. Even at 35 yearsold, the standard V35 Bonanza is verycapable. An airplane with a service ceiling above 16,000 feet, cruise speedsabove 165 KTAS,and a still-air range ofmore than 750 nm (on 74 gallons) is cer-
AOPA PILOT· 89 •MAY 2001
AOPABONANZASWEEPS
tainly very useful, but the installation ofa turbo normalizer transforms this goodairplane into a great-indeed, a twentyfirst century-airplane.
A turbonormalizing system collectsengine exhaust gases that are normallypumped overboard. These gases areused to indirectly drive an air compressor. This compressed air artificially creates sea-level atmospheric air pressureswhen it is pumped into the engine. Inthis way the engine can develop fullpower (300 horsepower) at altitudes upto and above 20,000 feet ms!.
The building blocksA turbocharger consists of an exhaustgas-driven turbine wheel in a cast-ironscroll housing and a compressor wheelin an aluminum scroll housing, withboth wheels mounted on a common
rotating shaft. The housings, the shaft,and the two wheels make up the turbocharger assembly. The center shaft issupported in a bushing that is constantly lubricated by circulating engineoil. The turbocharger is a component ofthe turbo normalizer system.
The Tornado Alley Turbo WhirlwindII system replaces the original exhaustsystem with a heavy-duty stainless steelsystem. Exhaust gases are collectedfrom the engine cylinders and are routed to the turbine wheel inlet.
At low altitudes, where the air isdenser, the compressor doesn't have tocompress a lot of air to maintain themanifold pressures necessary for the
Cool ram air enters the intercooler housingthrough the orange flexible ducting. Compressed air from the turbo, now cooled, exitsthrough the black hose to enter the engine.
engine to produce 55-percent to 75-percent power. As the airplane climbs, theair pressure decreases, so the compressormust deliver more air. A turbonormalizer
system increases the amount of compressed air that is delivered to the engineby controlling how much of the totalexhaust gas bypasses the turbocharger.This bypass route is controlled by a butterfly valve called a wastegate. Closingthe wastegate increases the amount ofexhaust gases being forced past the turbine wheel. The resultant higher rpm ofthe turbine and compressor wheels
increases the amount of compressed airdelivered to the engine.
In this system the position of thewaste gate is controlled by the absolutepressure controller. This controllermonitors the pressure from the compressor output and maintains a constant air pressure in the "upper deck" ofthe system by adjusting the position ofthe wastegate.
The upper deck is the part of the turbonormalizer system that is locatedbetween the compressor outlet and theengine throttle plate. The controller isdesigned to maintain the upper deckpressure at two to three inches of pressure above the maximum manifold
pressure the engine would ever need.This type of system works the turbocharger a little harder than some "ondemand" systems, since the components of this system are adjusted toalways maintain 33 to 34 inches ofupper deck pressure, but this is offset bythe fact that there's never any turbocharger lag or spool-up time. A pressure relief valve (pop-off valve) ismounted in the ducting between thecompressor outlet and the engine, andis designed to open if the controllermalfunctions and allows upper deckpressure (and consequently manifoldpressure) to increase beyond safe limits.
Looking through the lower left engine accesspanel, the sliver scroll of the compressorside of the turbocharger can be seen. Filtered inlet air is delivered to the turbo via
ducting from the front of the engine compartment. The compressed-air ductwork can
be seen exiting the top of the scroll.------------------------------------------------~r_AOPA PILOT' 90 •MAY 2001
The system operation is simple. Thepilot adjusts the throttle to select themanifold pressure he wants, and thesystem automatically maintains a constant upper deck pressure, which maintains a constant manifold pressure.
IntercoolerCompressing air raises its temperature.Since we would like the air to be sealevel dense, and as near standard temperatures as possible, sophisticated turbonormalizing systems have an air-toair radiator in which the heated, compressed air from the compressor iscooled by ram air before it enters theengine. This device is called an intercooler, and the Tornado Alley Turbo system has a very efficient one mountedbelow the engine on the right side.
After the initial acquisition costs of aturbonormalizing system, are there anyother costs involved? Yes, there will beslightly higher costs associated with aturbo normalizer system, especiallyduring an engine overhaul, when the
high ambient temperatures or high airport elevations are simply no longera problem.
Before Tornado Alley TurboIn 1994, AOPA Pilot reported on flyingGeorge Braly's turbonormalizerequipped 1967V35 from Orlando, Florida, to Ada, Oklahoma (see "HigherFlyer," March 1994 Pilot). Braly startedTornado Alley Turbo Inc. after acquiringthe turbonormalizing STCs for theBeech Bonanza and the Cessna 185from FliteCraft Turbo, of PagosaSprings, Colorado. Before Tornado Alleyupgraded the original FliteCraft installation, cylinder head temperatures(CHTs) in Braly's Bonanza often exceeded 400 degrees Fahrenheit duringclimbs to altitude. Low-altitude performance also suffered when ambienttemperatures were high.
Braly, an engineer by training, cooledthe installation down with the Whirlwind
II upgrades. Changes include a new composite airbox and alternate air door relo-
Lean-of-peak operations, if correctly performed by
the pilot, result in lower temperatures than
rich-of-peak operations.
turbo components (including theexhaust system) should also be overhauled. The Tornado Alley system isdesigned for long life, uses proven components, and shouldn't have any trouble matching engine TBO numbersbefore needing overhaul.
Some new powerplant managementtechniques (we will get to TornadoAlley's method in a moment) will haveto be adhered to, and the pilot will haveto learn about hypoxia, the use of oxygen, and high-altitude operations. Is theengine overworked or stressed becauseoLthe installation of a turbonormalizer?
The potential exists to abuse a turbonormalized engine, primarily if the pilotalways insists on going as fast as possible. As pilots get used to the system,they will learn that a turbo normalizedairplane can easily climb above thethick, draggy air of lower altitudes towhere even conservative power settingsyield impressive speed gains. TAT likesto tout the advantages gained from itssystem at lower altitudes. True airspeedsare increased, and safety margins riseas power-robbing conditions such as
cation, a cooling kit for the number-2 andnumber-6 cylinders (this mod cools thesetwo cylinders by 30 to 35 degrees), cowllouvers adapted from currentA36 Bonanzas, and a set of baffle louvers to enhancecooling airflow past the cylinders.
The original intercooler has beenreplaced with a more effective "Rammer" unit that, combined with changesin the under-cowl plumbing and clevertricks such as recessing the landing lightfor more airflow, has effectively doubledthe volume of air passing through theintercooler. The result is improved hotweather takeoff performance, coolerCHTs, and safer detonation margins. Allof the Whirlwind II upgrades can beretrofitted to earlier installations.
The TATmethodof powerplant managementThe Whirlwind II upgrades include a setof turbo GAMIjectors (Braly is also thechief engineer at GAMI). GAMIjectorsare flow-matched fuel-injection nozzlesthat equalize the power output amongall cylinders. Tornado Alley believesthat long engine life is directly related
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to maintain the target temperatures.If any CHT goes above 380 degreesduring the climb, the mixture is adjusted as necessary to bring the CHT backdown to 380.
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The TATcruise
Cruise engine management consists ofrunning the mixture lean of peak(LOP). This is accomplished after leveling out, closing the cowl flaps, andaccelerating by performing the bigpull. The big pull consists of grabbingthe mixture knob and smoothlypulling it back until the fuel flowneedle is indicating approximately ISgallons per hour on the lean side ofpeak. After a short period of time, themixture is slowly richened until peakEGT is found, and then leanedagain until the turbine inlet temperature is approximately 80 degrees F leanof peak.
Up until GAMl came on the scenewith its finely tuned fuel-injectionnozzles that made lean-of-peak operations practical, the most acceptedpractice was to run one of theseengines with the mixtures set somewhere between 100 to 50 degrees richof peak to keep temperatures down.According to extensive testing by Tornado Alley, its method keeps TIT, EGT,and CHT temperatures even lowerthan rich-of-peak methods, and TATbelieves cool temperatures are the keyto long engine life. In spite of a greatdeal of solid evidence to supportGAMI's methods, not everyone is con-
AOPAwould like to thank the following companies that donated ordiscounted their products and ser-vices to refurbish the SweepstakesBonanza or otherwise assisted inthe project.
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from sea level to 10,000 feet; 1,260 to1,280 degrees from 10,001 to 17,000feet; and 1,240 to 1,260 degrees (withengine rpm increased to 2,600 rpm)when climbing above 17,001 feet. If theTAT procedure is followed, climb speedtargets are 115 to 120 KIASup to 10,000feet, 115 KlASup to 17,000 feet, and 105to 110 KlASabove 17,000 feet.
Because the system's automaticwastegate controls the engine manifoldpressure, and the prop governor controls the engine rpm, the pilot's workload is reduced to flying the airplaneand adjusting the mixture as necessary
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AOPABONANZASWEEPS
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to lowering engine temperatures. As aresult, each new owner of a TornadoAlley system undergoes training in howto fly the TATway.
The TATmethod of setting power forclimb involves setting the throttle wideopen, reducing the prop rpm to 2,500after the airplane is cleaned up forclimb, and then using the mixture control to adjust the turbine inlet temperature (TIT) to a target temperature. Thetarget TITs are 1,280 to 1,300 degrees
1
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i Links to additional information aboutthe AOPA Sweepstakes Bonanza may
be found on AOPA Online (www.aopa.org/pilot/links.shtml). Check the Web site .
(www.aopa.org/sweeps) for weeklyupdates on the project. E-mail the authorat [email protected]
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The resultThe TAT method of climb and cruise
operation is designed to keepcylinder headtemperatures below 380 degrees F.This is a full 80
degrees below themanufacturer's
fuel burn of 18.5 gallons per hour.The hottest cylinder head temperature was 358 degrees F during the215-KTAS flight.
The Carl GouletMemorial Test CellBraly and his staff in Ada, Oklahoma,have built one of the most sophisticated airplane engine test cells on theplanet. Rather than guessing whatgoes on inside the combustionchamber, they devised a way to sample the combustion chamber pressures and display a smorgasbord ofdata from their test-cell engines. Whathave they learned? That lean-of-peakoperations, if correctly performed bythe pilot, are safe, result in lower temperatures than rich-of-peak operations, and do not result in destructivedetonation.
These facts are borne out by yearsof test-stand study. For a look atTAT's plans for the future-and youcan bet they're not resting on theirlaurels-go to the Web site (www.taturbo.com). If you want to take alook at some of the data being gathered, go directly to the test-stand Website (www.engineteststand.com).
vinced. Sometimes this is because of a
reluctance to let go of old ideas, andsometimes it's because opponentsdon't realize how thoroughly GAMIand TATtest their ideas.
Why turbonormalize?Turbonormalizing expands an airplane's operating envelope. Becauseample power is always available,climbing up out of icing temperaturesbecomes possible. When selecting acruise altitude there's a whole band of
airspace between approximately10,000 and 17,500 feet where traffic isgenerally light. because it's too highfor normally aspirated airplanes andtoo low for turbine-powered airplanes. One result is that direct IFRflight plans are often approved. Again,this translates into a more efficient
way to fly.The turbo normalizer, because it
can easily provide sea-level manifoldpressures up to flight-level altitudes,allows the pilot to pick up some "free"airspeed by climbing up to altitudeswhere the atmospheric drag isreduced. The combination of less
drag and robust power results inhigher true airspeeds, and onlyslightly higher fuel-consumptionnumbers. During the first testing andadjustment flights of the sweepstakesBonanza, true airspeeds of 215 knotsat 17,500 feet were observed with a
AOPA PIl.OT· 93· MAY 2001 WRITE IN NO. 36 ON READER SERVICE CARD