whirlwind also powered some Americantanks.) BT-13s powered by Wright radialsare designated as BT-15s.Otherwise, the -13and the -15 are virtually identical.

In 1944 when production halted, 11,538BT-13s and -15s had been built. These

included 1,800 SNVs, the Navy's desig­nation for the Valiant. This also is when

military students began bypassing basicflight training and went directly from pri­mary to advanced.

The aircraft featured on these pages,U.S. Army Air Corps No. 41-1037, is aWright-powered BT-15 built in May 1941.It served at several California trainingbases until 1943,after which it had a num­ber of civilian owners. It was donated tothe Commemorative Air Force in 1979and

assigned to the CAF's Dallas-Fort WorthWing in 1989.It is based at the LancasterRegionalAirport in Lancaster, Texas,a farm­ingcommunitysouth of Dallas.N69605 fliesin airshows and has the same high-visibilitypaint scheme used to identify student pilotsduring the war. The solid red circle within "the insignia indicates thatthis is a pre-PearlHarbor paint scheme; it was removed fromU.S. aircraft after the Japanese attack toavoid possible confusion with the solid red"meatball" used on Japanese aircraft.

During World War II, military stu­dent pilots received primary training andtook their first lessons in any of severalopen-cockpit trainers: the Stearman PT-17Kaydet, Ryan PT-22 Cadet, or FairchildPT-19, -23, or -26 Cornell. They earnedtheir wings after completing advancedtraining in the venerable AT-6.

Sandwiched between primary andadvanced training were 10 weeks of basictraining that invariably involved the Valiant.It was by far the most popular basic trainerof the war and provided basic training to themajority of military pilots. When you hearsomeone refer to the BT,they likelyare talk­ing about the BT-13.

The Valiant was manufactured byVultee Aircraft in Downey, California. Thecompany was named after Gerard "Jerry"Vultee, and the airplane was designed byRichard Palmer. It first flew in March 1939,and deliveries to the Army Air Corps beganin June 1940. The Valiant was powered bya nine-cylinder, 450-horsepower Pratt &Whitney R-985 radial engine.

When the Connecticut engine makercould not keep up with demand, Vulteebegan to also use the Wright Whirlwind, the440-horsepower version of the engine thatpropelled the Spirit ofSt. Louis to Paris. (The

THE FLAP-CONTROL handle(above, lower left corner) isrotated to extend and raise theslotted wing flaps. The forwardcockpit of N69605 (right) is abit scruffy but provides a senseof nostalgia and history datingback to when this airplaneentered military service in themonths preceding the attackon Pearl Harbor. When thepilot moves the propeller-pitchcontrol forward, oil pressurefrom the engine pushes thecylinder forward (above),twisting the blades into lowpitch. When he moves thecontrol aft, the cylinder isrelieved of oil pressure andmoves rearward, enabling thecounterweights to twist theblades into high pitch.

52 I AOPA PILOT February 2013

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54 I AopA PILOT February 2013

These two excerpts are from the Army Air Force's Student's Manual for the BT-13:ONE: "Mark Twain wrote that 'a pilot must have a memory developed to absolute perfection,but there are two higher qualifications [that] he also must have. He must have good and quickjudgment and decision, and a cool, calm courage that no peril can shake.' Twain was not writingof airplane pilots but of men who steered Mississippi River sternwheelers that often attained theterrifying speed of 14 mph."TWO: "When lost. a pilot can determine his location using a dangerous maneuver that must beperformed with extreme care. The names of towns are almost always painted on both ends ofrailroad stations in large letters. The object is to fly by a station and read the name of the town.Your instructor will explain and demonstrate how this is done."(Author's note: When lost. a pilot also can search for and land at a nearby airport. He can thendetermine his location without the embarrassment of having to ask where he is by purchasingfuel and looking at the receipt to see the name of the town where he has landed.)

wheel also could be spun manually by aground crewman using a crank when thebattery was low.) The pilot then activatedthe mesh switch. This engaged the flywheelto the engine, and its inertia turned theengine. Hopefully, the engine started beforethe wheel's inertia was dissipated, other­wise the process was repeated. (A video ofa BT-13 starting inertially is available onYouTube. Search for "BT-13 Startup.")

The engine should be started withthe propeller in high pitch. After engineoil pressure increases, the prop control ismoved forward. Engine oil pressurizes thepropeller cylinder, which moves the bladesinto low pitch. This procedure ensuresthat the entire oil supply is available tothe engine during start and that relatively

Before soloing a BT,a student had to sitblindfolded in the front cockpit and unhesi­tatingly place his hand on any of 33controlsand switches as his instructor called them

out. The rear cockpit had a curtain thatcould be pulled forward to surround aninstrument student and prevent him fromseeing outside during "blind" flight training.(There were no portable instrument hoodsin those days.)

Thankfully I did not have to endure theembarrassment of a blindfold test when

being checked in the BT by Russ Coonley,a CAF instructor-pilot and retired airlinecaptain (Continental Airlines and UnitedParcel Service).

The Valiant's cockpit is slightly smallerand laid out similarly to that of aT -6. It hasa conventional electric starter but manyoriginal BTs had inertia starters. Theseinvolved energizing a motor that spun aheavy flywheel to its maximum rpm. (The

A PAIR OF venturi tubes (top)provide the vacuum needed todrive an artificial horizon anddirectional gyro. The ruggedstructure (center right) behindthe front cockpit protects thepilots in the manner of a rollbarshould the airplane be flippedon its back during an errantlanding. Two ways to distin­guish a BT-13(lower right)from an AT-6 are its fixedlanding gear and the tallantenna mast on its nose.

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warm oil is used to change propeller pitch.The BT does not have an electric fuel

pump. To create fuel pressure for starting,the pilot moves up and down a wobble­pump handle located to the left of his seat.If the engine-driven fuel pump fails duringflight, the pilot must continually "wobble"the manual pump to keep the engine run­ning until after landing. The BT-13 wasequipped with built-in relief tubes. (That'smykind of airplane.) Its "artificial horizons"and "directional gyros" are vacuum-drivenby venturi tubes.

The Valiant has wet wings, each con­taining 60 gallons of fuel.Takeoffis made onthe fullest tank, but when the right tank isselected, only 43 of its 60 gallons are usable.The bottom 17gallons of the right tank is

considered reserve fuel and can be used onlyby selecting Reserve with the fuel selector.

Taxiing with an open canopy on a warmday with the rumble of the radial engine'sexhaust is delightful. Forward visibility overthe large nose, though, is poor, requiringS-turns on a straightaway to ensure that youdon't bump into something. The hydraulicbrakes and main landing-gear wheels arethe same as those on an AT-6.

The slotted flaps are extended using ahand crank between the seat and the left

cockpit sidewall. Each full rotation of thecrank lowers the flaps two degrees. Theaircraft has a flap-position indicator, butsome pilots prefer counting cranks. Setting20 degrees for takeoff requires rotating thecrank 10 times. Another way to set takeoff

SPECIFICATIONS

Powerplant IBT-13 Pratt & Whitney R-985,9-cylinder radial, 450 hpBT-15 Wright R-975 Whirlwind,9-cyllnder radial, 440 hpRecommended TBO I typically 1,500to 1,800 hrPropeller I 2-blade, Hamilton Standard,2-posltion

Diameter I 108 inLength I 28 ft 10 inHeight I 12 ft 4 inWingspan I 42 ItWing area I 239 sq ItWing loading I 19.9 Ib/sq ftPower loading I 10.5 Ib/hpDihedral I 7 degSeats I 2Empty weight I 3,375 IbEmpty weight. as tested I 3,560 IbMax gross weight I 4,745 IbUseful load I 1,370 IbUseful load, as tested I 1,185 IbPayload w/full fuel I 650 IbPayload w/full fuel, as tested I 465 IbMax takeoff weight I 4,745 IbMax landing weight I 4,745 IbFuel capacity I 120 gal

7201b

Oil capacity I 10.9 galBaggage capacity I 150 Ib

PERFORMANCE

Takeoff distance, ground roll I 750 ItTakeoff distance over SO-ft obstacle1,400 ItRate of climb, sea level I 1,050 fpmMax level speed, sea level I 183 mphCruise speed/range (no reserve)

(fuel consumption). 10,000 ft@ max.cont. power I 156 mph/340 sm

(198 pph/33 gph)@ normal power I 146 mph/550 sm

(162 pph/27 gph)@ max. range I 123 mph/790 sm

(90 pph/1S gph)Service ceiling I 21,650 ftLanding distance over SO-ft obstacle1,300 ItLanding distance. ground roll I 650 It

LIMITING AND RECOMMENDED AIRSPEEDS

VX (best angle of climb) I 80 mphVy (best rate of climb) I 90 mphVGLIDE I 90 mphVFE (max flap extended) I 120 mphVNE (never exceed) I 230 mphVLIFTOFF (rotation) I 70 mphVS1 (stall. clean) I 72 mphVso(stall, in landing configuration) I 62mph

All specifications are based on maf/u­facturer's calculations. All performancefigures are based on standard day, stan­dard atmosphere, sea level, gross weightconditions unless otherwise noted.

THE AIRCRAFT featured here is U.S. Army Corps No. 41-1037,a Wright-powered BT-15 built in May 1941. It was donated tothe Commemorative Air Force in 1979.

flaps is to move the control stick fully leftand rotate the crank until the flaps areextended as much as the right aileron isdeflected downward. Such "matching" isnot recommended when airborne.

Takeoff is made with full throttle using36 inches of supercharged manifold pres­sure and 2,250 rpm. The takeoff is noisyfor bystanders because the propeller tipsexceed the speed of sound. The BT leavesthe ground at 70 mph and climbs best at 90.

Once established in the climb,pull the throttle back about aninch. Then pull the propeller-pitchcontrol fully aft. The airplane has a two­position propeller, not a constant-speedpropeller. It can be set only to a low pitchof 12.5degrees (for takeoff) or a high pitchof IS degrees (for climb and cruise). Thereare no intermediate positions.

It was easy (for me, anyway) to inad­vertently grab the mixture control and try

bringing it fully aft after takeoff (instead ofthe adjacent prop control). Fortunately, themixture control has a ratchet that preventsthe airplane from becoming suddenly quiet.(The ratchet can be bypassed when needingto lean the mixture.)

After setting the prop to high pitch (lowrpm), all subsequent power changes aremade using throttle only.Set to low or highpitch, the propeller behaves as if it were afixed-pitch propeller-which, in a sense, itis. Just like when flying with a fixed-pitchpropeller, increasing airspeed increasesrpm, while decreasing speed reduces rpm.

The flight controls are responsive andreasonably well harmonized, but the aile­rons are a bit heavy even though equippedwith servo tabs, a form of aerodynamic

power steering, to reduce stick forces. TheBT doesn't seem to have any undesirabletraits, but when stalled-even with theslip-skid ball caged-it falls off on a wing.

Recovery,however, is easy and conventional.The yellow band of the tachometer,

1,350rpm to 1,650 rpm, should be avoidedduring an approach to landing. Otherwise,you quickly learn why the Valiant wasaffectionately called the Vultee "Vibrator."Some claim that this nickname resulted

from the BT's tendency to shake violentlyas it approaches a stall, something I did notnotice. Others say that the canopy vibratesduring aggressive maneuvering. It has beensaid, too, that a BT takeoff causes windows

on the ground to vibrate.The airplane can be landed with 60

degrees of flaps, but this makes touch-and­go landings and missed approaches moredifficult because of the enormous drag.Having to crank the handle to raise the flapsat such critical times can be challenging.Landing with 40 degrees is more practical.The Vibrator is a joy to land either on themains or in three-point attitude.

By the end of 1948 there were 4,000surplus BT-13s and -15s in civilian hands.There was one at almost every airport, butthey were expensive to maintain. Manyowners abandoned their aircraft after

their engines had run out. Other BTs werepurchased for their engines, and nakedairframes were abandoned or scrapped.

Although there are now 300 registeredwith the FAA, only about 40 remain air­worthy. A few BTs were modified to looklike Japanese torpedo bombers and usedin the motion pictures Tora! Tora! Tora!and Pearl Harbor. These aircraft alsoare used in battle reenactments atairshows.

The author dedicates this article to those

thousands of airmen who trained in the

Vultee Vibrator as they prepared to.". ,¥i

their country.