April 1999 - American Bonanza Society

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We're running out of column spacebefore we get to the bottom of our avionicsstack. We haven't even discussedthe DME, which operates in the UHFband, the transponder, which operates at1090 MHz. and about which I'll say moreabout, the ADF, as we all know is lowfreq uency, 200 KH z to 1600 KH z.Stormscopes and Strikefinders are alsolow frequency. Radar, for those of us whohave it, are in a superhigh frequency bandwhich is ca ll ed GlGTHERTZ or GHz.How about the electrical stuff on ourairplane that we don 't even think of astransmi tting a radio signal until we gochasing it?There's alternator noise, magnetonoise, inverter noise, remote compassnoise, autopilot noise. landing gearand flap motor noise.I guess the strangest one I ever encounteredwas Mylar-American-flag-o nthe-rudder noise! The flag was mountedon the rudder just above the NAV antenna.The aluminum-backed flag wasmounted over a fresh paint job. The flagacquired a static charge that it could notdissipate through the paint to ground. Thestatic charge fi nally got so powerful itcaused the AV left/right needle to "hunt"back and fonh. See you next month.ABS member Jim Hughes holds a BS degreein Aero Engineering. l-le is a CFII and an A&Pmechanic. Jim heads Marketing & Profes siolla/ Services, a consulting and flight-restfirm involved in bo th military and civil avionicsapplications.P-FACTORBY HEN RY W DAVISONLinthicum Hts., MarylandP-factor is a phenomenon in volvingthe propeller that occurs whenever the enginethrust-line vector does not coincidewith the airplane fl ight path. In one example,such is the case when the airplaneis in Slow-flight profile. With this profile,the descending blade achieves itshighest effective pitch angle while passingthrough the horizontal position. Conversely, the ascend ing blade is at minimumeffective pitch when horizontal.Simply put, P-factor amounts to unequalthrust of one propeller blade comparedwith the other(s) at any given pointthroughout a revolution cycle. The endresult translates into an effect on the propellerplane of rotation that is visualizedas a solid disc. This unbalance in thrust,called asymmetric propeller disc loading,displaces the center of thrust from theaxis of rotation. As a consequence, thisphenomenon obviously the lack ofrudder causes yaw when uncorrected byconrrol input. Secondly, it causes inefficiencyin propeller and airplane performance,especially at high angles of attack.Mush angleP-factor has a direct relationship to thewing angle of arrack beyond the angle ofPage 5661incidence or the angle between thelongitudi nal axis and the fligh t path.Aerobatic maneuvers, such as the knifeedge or invel1ed flight, amplify this mushangle when sustained flight depends onexcessive speed, fuselage lifting bodyeffect and the oblique thrust vector. Thegreater the mush angle, the more dominantP-factor becomes, up to the threshold ofblade stall.Resultant relative windThe difference in thrust in the variousblade positions is the result of tluctuatingangle of attack accountable to bladeangle and resultant relative wind.The resultant relati ve wind or infl owair is conceived from two relative windcomponents: one by virtue of propellerrotation. the other by airplane flight path.In reviewing the definition, relative windis wind created by motion of an object andacts directly opposite to the direction ofmotion. A resultant relative wind is the averageof the two relati ve wind components.Because the blade leading edges areopposite from each other (when horizontal,one ide faces down; the other sideup), the resultant rel ati ve wind exposesthe descending blade to a headwind advantage.The oppos ite si de blade, however.experiences a reduction in headwindbecause of the greater span between thetwo relative wind components which altersthe average wind vector. While theflight path relative wind component is farless prominent than the rotational windcomponent, the differential effect in airspeedis significant enough to contributeto the thrust dilemma.Additionall y, the blade center of pressureconstantly changes wi th blade angleof attack. Like the wing, center of pressuremoves forward when angle of attackincreases, and aft when it decreases. Consequently,the variable drag componentinfluences the other resultant forces.P-factor - light twin airplanesAs the saying goes: "When you losean engine on a light twin, you lose 50percent of power and 80 percent of performance."Consequently, slow flight becomesautomatic-and P-factor comeswith the territory. On a twin that both enginestum clockwise, losing the left engineis more critical to night than losingthe right. as far as P-factor is concerned.The asymmetrical disc loading on theright engine propeller is fUl1her from theairplane CG than that fo r the left enginepropeller. With a greater leverage on theright engine, the minimum si ngle enginecontrol speed (Vmc) increases when theleft engine is out.With counter-rotating engi nes, the leftengine turns clockwi se; the right enginecounterclockwise. The leverage effect isthen minimized.SummaryWhen analyzing the P-factor phenomenon,one can concl ude that propeller performanceis far less than expected, especiall y when climbing out at high angleof attack at low altitude. Pan of the art offlying is knowi ng where the imaginaryboundary of safe operation exists in thatmoment of tru th.ABS Apri I 1 999
Shop TalkBY LYNN JENKINSRaytheon tackles theproblems found in the1998 A36 N41 NHAt the request of ABS member FrankGlenn (who was taking deli very of abrand new 1999 BeechA36 Nl2FG SINE-3219) and the following Raytheon personnel-Don Cary, Director/CustomerRelations, and Brad Stancil, VP WorldwidePi ston Sales- I was invited toRaytheon to take a look at Frank 's newA36 prior to delivery along wi th an opportunityto review with Engineering theimprovements and changes that are nowbeing made to the 1999 line of pistonaircraft: Bonanzas and Barons. (See "Bonanzaofthe Month" article on page 5637.)If you recall, about a year ago I hadan opportunity to look into a brand newA36 while it was opened up for an av ionics installation . Following that, I wasonce again able to look over the aircraftduring its first annual inspec tion. Someof the things we found with the aircraftwere very disturbing, so we published ourfindings in our July and November 1998"Shop Talk" articles.ABS April 1999Raytheon took our findings very seriouslyand put together a program to addressthose issues as well as other itemsthat were on the back burner in their 1999piston aircraft. The man responsible foraddressing Engineeri ng, Quality and allother associated projects with the pistonline of Beech products is Steve Young,Director, Piston Business Unit.During my two day stay at Raytheon,Mr. Young must have spent six or morehours of hi s very valuable time go ingover changes they had made to improveand clean up the known problems withearlier Beech aircraft. To say the least, Iwas very impressed with what they hadaccomplished.A written copy of all of the issues includingthe action taken or pending wasgiven to me.The following responses are copied directlyfrom Raytheon's internal document:ISSUE: Windscreen covered with fine oilspray on it (prope ller or the engine nose seal).ACTION: Oil comes from the prop-seal hasto sell!, then spraying goes away.ISSUE: Aircraft delivered with two keyskeyedthe same-neither key worked in thecabin door.ACTION: Redesigned door locks and newkeys effcctive with E-32 18. EA-629 andTH-1883.ISSUE: Right rudder cable was cutting intothe bmke hydraulic line where it enters the parkingbrake control module. (Removed floorboards under pilot·s feet.)ACTION: Redesigned cable layout and creatednew P 36-58000 1-27/-29; Effecti veon E-3212 and EA-628.ISSUE: Removed side panels and foundlarge amount of alumi num shavings behindthem- a lot of material.ACTION: Foreign Object Encroachment(FOE) Program in place in Plant II.Note: Side panels are now routinely removedand vacuumed after dri lling. Also aircraft isvacuumed several times a day.ISSUE: Cross brace stringer th at holds thecable guide has been kinked and bent. (Removedthe interior rear panel for access tothe inside of fuselage.)ACTION: Employee training required. Accessplatforms used to work in back of aircraft.ISSUE: The taxi light mounted on the nosegear was set for stargazing. ft was necessaryto adjust the spacer shims so the light wouldpoint down the taxiway.ACTION: Ran conformity. Had thick washersbetween the retainers and the base andthere wasn't supposed to be any washers perblue prim- now wi thout washers.No te: When we took delivery of FrankGlenn's aircraft, the taxi light was still lookingfor Klingons near Deep Space Nine.Steve Young plans {Q take an aircraft fromthe production line and do night taxi testswi th it.ISSUE: Fuel dripping out of fuel drain . Theright main tank fuel drain was leaking.ACTION: Vendor recall (improper staking)Anything found in fie ld, we are changing.ISSUE: While in flight, the right forward topwing attach bolt cover plate came loose. Theclip that holds the plate flush with the wingwas broken.ACTION: Increased inspection during assemblyand deli very.Note: The plates are still being glued to tbewing root mo ldi ng. This is an inspection plateand should not be glued at fabrication to thewing root moldi ng.ISSUE: The plastic access door located behindthe copilot 's right leg on the right sideof the spar cover does not close securely. Thefastener is just floating in the hole rather thanbeing sec urely mounted to the spar cover.ACTION: Manufacturin g and Inspectionalerted to veri fy U-shaped clips are installed.ISSUE: Here is an item that adds to yourmaintenance expense. In order to remove the24-volt battery from the battery box compartment,it is necessary 10 unbolt the battery boxfrom the fire wal l. Rather than being a hingeddesign, it is necessary 10 remove five boltsto extract the battery box.ACTION: Evaluating possibilities of a redesign.ISSUE: There is a drain tube located at the bottomof the coupling (ducting) between the airbox and the fuel controller (intake housing).The hose coming from the drain filling wascompletely kinked off so thm no fuel or watercould flow overboard from the drain tube.ACTION: Th is has been a problem in thepast but Manufacturing and Inspection hasbeen alened and we have not found this onany recent aircraft.NOle: During my factory tour wh ile atRaytheon, I looked at several of these draintubes and found all of them to be installedcorrectly.Page 5662
Page 4: APRIL 1999~(ISSN 0161-3545)Publishe
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Page 20 and 21: InsuranceBY JOHN ALLEN, PRESIDENTFA
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Page 26 and 27: AvionicsBY JIM HUGHESW.hy you can't
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Page 36 and 37: LEESBURG. VIRGINIA, HAS MANY GREAT
Page 38: C a I e n d a rAMERICAN BONANZA SOC

April 1999 - American Bonanza Society

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