bushby mustang ii aircraft performance report - CAFE Foundation

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fort on sunny days. With a little practice,the view through this wassufficient to see other traffic.In this Mustang II the oil temp consistentlyran below 180 degrees. Evenafter sustained periods of slow flightthe temperature only came up to 185degrees. No cowl flaps are available,nor do they seem necessary. No climbcooling test was performed.STATIC LONGITUDINALSTABILITYUpon leveling off at 7,000’ and 120mph IAS the first task was to explorethe static longitudinal stability. Withthe airplane trimmed to 120 mph ahand-held stick force gauge was usedto measure the elevator force requiredto hold level flight. Each airspeed, in10 mph increments throughout theentire speed range, was evaluated byadding or reducing power as necessaryto alter the airspeed. The elevatortrim remained unchanged throughoutthis test. The greater the incrementalforce at each successive airspeed thegreater the static stability. Havingflown a variety of other similar airplanesand previously submittedreports on the RV-6A and the Tailwindit is my opinion that the MustangII has one of the best stick force gradientsfor all-around flying. See Figure1.DYNAMIC STABILITYDynamic stability, short period, inboth stick-fixed and stick-free modeswere explored. A sampling of all airspeedsacross the entire operatingrange were tested in both modes. Theresults were completely ‘deadbeat’, inthat when pitch doublets were inducedand the stick was then let free,no pitch oscillations or overshoots resulted.This is evidence of the idealdynamic stability qualities with thisdesign.I was unable to fully trim the elevatorto airspeeds below 110 mph IASdue to the limited travel of the electricelevator trim system.SPIRAL STABILITYMUSTANG II APRNormally my evaluation of spiralstability would be done at both 90 &120 mph IAS, however, due to the inabilityto fully trim the elevator to 90mph I could only evaluate its performanceat 120 mph. After carefullytrimming and stabilizing in a 30 degreebank turn, the controls were releasedat which time I observed thebanking tendencies. After more than40 seconds of continued turn with nochange in the bank attitude, the testwas terminated. The Mustang II thusexhibited neutral spiral stability inboth directions. A feature such as thiswould be beneficial to a pilot duringmoments of inattention. The MustangII gives the feel of lightness on thecontrols, yet is not an airplane thatyou have to watch constantly to keepit under control in bank. The airplanetends to stay in the existing attitudeunless control inputs cause it tochange.ROLL DUE TO YAW86420-2-4-6-8Tailwind, 120 IASCessna 152, 100 IASMustang II, 120 IAS70 90 110 130 150 170IAS, mphFigure 1.Static Longitudinal StabilityTrimmed hands-off at VaRoll due to yaw, at Va and 1.5Vso,was examined by inducing steady stateyaw with the rudder and observing thebank required to hold the airplane ona constant heading. The results weresimilar at both airspeeds examined(90 & 120 mph). half rudder deflectionrequired 8-10 degrees of bank tohold a constant heading. Full rudderdeflection required 15 degrees of bank.The 90 mph test was repeated withfull flaps extended. Here, only 5 degreesof bank with half rudder, and 10degrees with full rudder deflectionwere needed.Another way to look at the roll dueto yaw or dihedral merits of an airplaneis to observe the bank whileinducing yaw with the rudder (handsoff the ailerons). This plane shows astrong and positive tendency for thebank to follow the yaw input. Withrudder alone the bank could be controlledfrom 30 degrees of bank in onedirection to 30 degrees bank in the oppositedirection. It was during thesechecks that I noticed that the airplaneexhibited a stronger than normal tendencyto oscillate in yaw. I decided tofurther investigate this during theDutch roll check later in the flight.ADVERSE YAWAn adverse yaw estimation wasmade by slowing to 80 mph and, usingfull aileron, observing the hesitationLarry FordThe cowl exit area was reduced by70% to cut cooling drag.
MUSTANG II APRPowerDrawof the heading at the onset of the turn.With the short wingspan and quickroll it responded as anticipated withvery little adverse yaw. Even the mostdramatic aileron inputs yielded only 5degrees of heading change opposite tothe roll input.ROLL PERFORMANCERoll rates were also measured at120 mph through the use of a wiregrid attached to the instrument paneland a stop watch. The right to left rollrate was 72 degrees per second, whilethe left to right rate was 66 degreesper second. Figure 2 compares theroll performance of other aircraft wehave tested.DUTCH ROLLDutch roll was examined by inducingdoublets in yaw, pitch, and roll.Upon release of the controls the oscillationcontinued much longer thannormal for an airplane that had justexhibited such otherwise strong stabilitycharacteristics. Upon furtherexploration I found that with rudderalone I could excite yaw oscillationsthat would continue for as many as 15overshoots. At no time was it severeenough to present any danger. It wasjust that the directional stability wasnot as strong as it was in roll andpitch. The oscillation could be easilycontrolled with the use of the rudderas a yaw damper. It exhibited noDutch roll tendencies.STALLSThe stall sequence was very interestingto evaluate. At 1300 rpm, toapproach the stall slowly, the airspeedwas reduced while looking for any signalof an impending stall. There wasno electronic stall warning system installed.In flaps up configuration, thestall occurred a b r u p t l y with virtuallyno aerodynamic buffeting or warning.The nose just crisply and abruptlypitched down with mild left wingdrop. The recovery was instantaneouswith the release of the stick back-pressure.Several stalls were made withexactly the same results each time.The 60 mph panel indication of stallwas consistent but will be checked forROLL RATE, degrees/secondSpeed, IASRV-6ATailwind W10Cessna 152Mustang IIVa80474772Figure 2. Roll rates include theaileron input time.1.3 Vso364534naBrien Seeleyaccuracy on later CAFE flights.Flaps were extended for comparisonof the landing stall characteristicswith those of the clean stall. It wasdifficult to fully extend the flaps to thethird notch until the airspeed was below85 mph. The handle could bemoved to the proper position but itwould not lock into the notch and stayextended. The stall with full flaps occurredat a panel indication of 63mph, 3 mph higher than with no flaps.The abrupt pitch down and left wingdrop were very similar to that of noflaps.Since the higher airspeed puzzledme, I checked the stall speeds at allflap settings. With two notches thestall was 61 mph and with one notchit was 60 mph. The quick recoveryand very predictable nature of the stallcharacteristics are pleasant and not aworrisome thing at all. However, ifone desired the buffeting stall warningof some of the production aircraft, thisplane would need some added devicesto create such warning.Without the barograph and otherinstrumentation installed, a maximumspeed run was made at 7,500’ for latercomparison with the instrumentedflights. The maximum IAS was 178mph @ 2750 rpm.MANEUVERING STABILITYFigure 3 shows a graph of the maneuveringstability or stick force per Gobtained. This is a measure of how
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