EAA Sport Aviation - August 2009

aircraft level by simply adjusting the air pressure in the tires. (Don’t forget to re-inflate the tires before flying.)

While you’re in the cockpit, the first thing to do is to ensure that the aircraft instruments are reading what the aircraft is actually doing. The turn and bank indicator and the attitude indicator should be showing the aircraft to be perfectly level. If they’re not, each instrument can be adjusted by loosening the front mounting screws and gently rotating the instrument to the correct position. I’ve heard of more than a few cases where pilots thought the aircraft was flying with a wing down, only to discover that the instruments were in need of adjustment.

The next step is to ensure that the fixed surfaces of the aircraft are in alignment. Using a tape or string that does not stretch, measure the distance from each wingtip to a point on the centerline of the tail cone. The same technique can be used to check the horizontal stabilizer by measuring to a central point at the front of the aircraft. Do not use the front of the vertical stabilizer or the spinner as a measuring point because many aircraft are designed with asymmetric mountings to help reduce P-factor. The left and right measurements should be equal. If they’re not, the aircraft may have been improperly repaired following an accident.

If your shop floor is perfectly flat, you may be able to measure the wing dihedral, but you’ll need to have access to the proper rigging tools to check the wing and tail angle of incidence. In most cases, you’ll find everything in order, but it always pays to check the fixed surfaces first, before spending time and money on the control surfaces.

7; 5;;5G TXKEG;%GPVGT;(NQ TKFC /6;2TQRGNNGT;75#;;+PE; 2JQPG;;;;;;;;;;;;;;;; KPHQ"OV;RTQRGNNGTWUC;EQO *GCFS WCTVGTU;KP;)GTOCP[ /6;2TQRGNNGT;'PVYKEMNWPI;)OD* 2JQPG;;;;;;;;;;;;;;;;;; UCNGU"OV;RTQRGNNGT;EQO Z Z Z ; P W ; S U R S H O O H U; F R P ,I ;\RX;DUH;ORRNLQJ;IRU;SHUIRUPDQFH;;ZH;VHOO;LW; (##;EGTVKſ;GF;J[F TCWNKE;QT;GNGEV TKE;EQPUVCPV;URGGF;RTQRGNNGTU;HQT;CNN;JKIJ;RGTHQTOCPEG;CK TETCHVU; +ORTQXGF;2GTHQTOCPEG; 7PNKOKVGF;$NCFG;.KHG; .GUU;8KDTCVKQP; .GUU;9GKIJV; .GUU;0QKUG;

0DQ\; 67&V;DYDLODEOH

Engine Alignment

As we stated earlier, many aircraft designs set the engine thrust line at an angle to help reduce P-factor. In most aircraft, this alignment is built into the engine mount design. However, if corrections are required, washer spacers are inserted, as necessary, between the rubber dampers (LORD mounts) and the engine case.