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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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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 steve.ells@aopa.org

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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