Tuesday, January 24, 2012

President's Squawk: Improving Flight Safety

Greetings Pilots: Let’s talk about Flaps

I can remember my first flight instructor explaining to me that flaps are like a speed brake that allows an aircraft to increase its rate of decent without increasing airspeed.  “This is an effective tool to use when a pilot intends to land an aircraft” he said as he went on to explain landing performance calculations. I understood the concept and proceeded to use flaps on my ensuing solo flight and private pilot check ride with little thought to the pros, cons and hazards of their use.  I believe that this is typical of most newly minted pilots so I would like to discuss a few issues related to flaps operations in IAA aircraft.

Flaps: Most of the flaps used in IAA aircraft are either “plain” or “slotted” with regard to structure and extension.  Typically the “plain” flaps are manually operated by simply moving a lever up or down in the cockpit which moves a rod on the top of the flap.  This rod pushes or pulls the flap around three hinge points on the wing which creates an extension (rotate down) or retraction (rotate up).  The slotted flaps are mechanically operated by an electric motor.  The motor moves a cable through a bell wheel assembly and connects to a rod which moves the flaps up and down on a track.  This is a more complex operation which involves more parts.

Our pre-flight inspections involve looking at the rod connection points to the flaps, the hinge points, the flap tracks and the rollers in the flaps tracks.  It is difficult to see the rollers move on the flap tracks as the pilot is in the cockpit when flap selections are made so whenever possible, attempt to have another pilot or guest move the flaps for you when you complete the inspection.  This will assure proper movement of the parts and avoid any ceasing/binding of the flaps which is very hazardous.

Flaps Operation:
Each aircraft manufacturer has recommended maximum and minimum flap operation speeds associated with the varying flaps settings.  Pilots need to observe these speeds as a “flap over speed” may cause flap torsion/binding or linkage separation.  This has produced “split flaps” or a “trailing flap” in IAA aircraft.  I cannot emphasize the magnitude that these flight hazards pose to an unprepared pilot.

Flap Performance: Some of the POHs associated with IAA aircraft suggest flap retraction immediately after landing to reduce the aircraft landing distance.  The intent is to apply additional traction to the tires for braking /friction.  I would like to stress to IAA pilots that this practice is meant for extreme circumstances and not condoned by IAA.  Maintaining aircraft position awareness on the runway is the most important task for the pilot after landing.  IAA would recommend the use of a runway that is 25% greater than the planned landing of the aircraft so extreme braking action would not be necessary.

Though time and lots of guidance from multiple instructors I have learned many flap tricks for take-off, decent and landing in various aircraft, and although I cannot put some of these techniques to print, I appreciate their effectiveness.  The use of  flaps is not easy and  their maintenance should not be taken for granted by any pilot.

Sincerely,

Robert Werderich, President
Illinois Aviation Academy, Inc.