COMANCHE TECH TALK

 WHAT IS "SNUGLY "?

by Omri Talmon

The one to ask such a question is Mr. Webster.  He defines "snug" (among other defitions) as, "fitting closely and comfortably," and snugly is an adverb.  What does it have to do with Comanche Tech Talk? Here is the answer.

The aircraft manufacturers went to the trouble of installing retractable gear in order to reduce drag and make our birds go faster.  In many aircraft, the gear retracts completely and is concealed in the wings or fuselage.  The Comanches are not so blessed: The nose gear goes all the way into the fuselage but the main gear is somewhat hanging down into the wind.  Not enough place for it in the wings.

It goes without saying that the higher the gear goes into the wings (with a limit, of course), the better. How to adjust it?

My Piper manual reads, "The main gear should be pulled snugly against the rubber stop blocks located in the wheel well".  Mr. Webster gave us the linguistic meaning, and here is how I translate it into mechanical terms.

When the aircraft is on jacks with the gear retracted, the initial act is to crawl under the wings and feel with the hand as well as visually check how tight is the gear against the said blocks. If it seems that there is a clearence between them, or there is only very little compression of the rubber, it is time to adjust the up position of the gear.

The first step is to disconnect the gear doors and secure all parts against getting in the way when the gear is moving up or down.  Then, we must check that there is enough room for the nose gear to retract higher. Normally, there is enough space. By the way, if there are tire marks on the nose gear doors it is another indication that the gear should come up some.

The up position is determined by a microswitch which is located in the gear well, and whose position may be adjusted. In later Twin Comanche models there is even a knurled nut so no tools are needed.  The position should be adjusted by small increments, and the gear retracted each time for control. It is recommended to use an external battery.

Back to the question: How much is snugly?  In addition to the visual check, it is possible to measure the electrical current drawn by the gear mechanism.  When it starts to rise sharply (of course being still below the rating of the circuit breaker), it is time to declare snugly.  Another very important indication is the force required to manually release the gear. If the system is too snugly, and under excessive tension, it may be difficult or impossible to release the gear. 

Caution: When practicing manual gear extensions on the ground, the gear should not be allowed to drop down all the way.  There is no wind pressure to slow and cushion it so the force of the drop may damage something.  A pile of tires under the main gear will provide a cushion.

Once the gear is snugly up, the microswitch should be secured, and then it is possible to proceed with the adjustment of the gear doors.  The main gear doors close against small rubber bumpers which very often pull a disappearing act, so it is time to take care of these as well.

A well adjusted gear is the cheapest speed mod available, and it is effective.

Omri Talmon, born in 1936, lives in Tel Aviv, Israel. He holds degrees in engineering, business administration and accounting. Presently a consultant, he worked for many years as an executive for several hi-tech companies.  Omri is a private pilot with both Israeli and U.S. certificates.  His ratings include SEL, MEL, Instrument, Glider, and CFI (glider).   Since 1974 he owns and flies a 1966 PA-30-B, registration 4X-CAO.