Archive for October, 2011

Wind gusts

Friday, October 21st, 2011

 Wind is defined by Webster’s dictionary as a strong current of air. Although simple in definition, the affects of wind on a helicopter can be profound. To a pilot who clearly understands this, wind can be very helpful. Yet, helicopter pilots sometimes underestimate the risks of flying in gusty wind conditions.

On March 27, 2002, the pilot of a Hughes 269 helicopter lost control while hovering at the Fort Collins Downtown Airport. The flight instructor reported that the wind was about 2 knots at takeoff, but forecasted to be gusty in the afternoon. While hovering at about 3 ft with the student pilot at the controls, the helicopter encountered a very strong gust and began to wobble. The instructor took control of the helicopter and climbed to about 15 ft when another gust hit the helicopter, turning it sideways and then downwind. The instructor stated he was attempting to get it on the ground, but the wind continued to drive the helicopter forward with excessive nose-over tendency. With the tail rotor into the wind, creating a high power demand and limited tail-rotor authority, the helicopter skipped along the dirt two or three times. The helicopter traveled forward 180-200 ft. The right strut failed, and the helicopter rolled over on its right side.

The instructor reported that he thought the wind was gusting to 60 knots at the time of the accident. The reported weather at the Fort Collins-Loveland Municipal Airport, 8 nm south of the accident site, was wind from 260 deg at 13 knots, gusting to 25.

Extra care should be taken when sitting on the ground with less than 100% rotor rpm in windy conditions. Wind can affect the flexing of a rotor blade at low rpm much more than at normal speed. An Enstrom 280FX helicopter was substantially damaged when the main rotor blades struck the tail boom while sitting on the ground. In an interview with the NTSB, the pilot stated he landed in a corn field and got out of the helicopter while the rotors were still under power. Then, he said a gust appeared and the main rotor severed the tail boom.

It should go without saying that leaving the pilot station of a helicopter with power still applied to the rotor system is just a really bad idea under any circumstances.

Helicopter instructors

Friday, October 7th, 2011

A certificated flight instructor (CFI) had his student were practicing hover taxiing before concluding the last of three flights in a Bell 47D–a model known for its docile flight characteristics and forgiving nature. The student had trouble that day maintaining rotor RPM during maneuvers, so the CFI looked inside to check as the student started to apply collective. When the CFI looked back outside, the helicopter was nose high and rolling to the right. He tried unsuccessfully to recover. The main rotor blades struck the ground. No one was hurt.

Due to the highly responsive characteristics of helicopters, the briefest bit of inattention by a CFI can result in an accident. This has haunted anyone who has ever worked as a CFI. Yet, in defiance of logic, we rely on the least-experienced pilots to do the vast majority of primary flight instruction. It should be no surprise that flight instruction has the highest accident rate among commercial helicopter operations.

One problem is that many pilots instruct just to build the time needed to get a better job. Competency as a CFI requires more than that. To be effective, it requires an interest in and desire for instructing. A CFI applicant needs only a cursory knowledge of teaching theory to pass the FAA’s fundamentals-of-instructing written test. It is a far more complex matter to understand how the mind processes information and learns, but a thorough understanding of this is what separates a professional teacher from a time-builder.

Flight instruction is demanding. A CFI must allow extremely inexperienced people to manipulate the flight controls, typically in a light, highly responsive, and unforgiving Robinson R22, in which most primary flight instruction is done. Instructors must continually weigh when the time is right to take over the controls. A student can benefit from correcting his own mistakes, but allowing a student to go too far might make the helicopter unrecoverable. Accident reports from the NTSB consistently list delayed remedial action and inadequate supervision as probable causes in training accidents. Such reports offer a wealth of information, and their complete review can be a great learning tool for CFI applicants.