CHI01LA215

The helicopter sustained substantial damage on impact with vehicles and terrain on takeoff following a reported in-flight loss of engine power. The pilot and two passengers sustained minor injuries. The pilot stated, "The fact that all was indicating normal, I re-confirmed power settings and we departed via a normal rate of climb takeoff. ... It was quite obvious very quickly the aircraft had momentarily suffered a partial power loss. I was not at sufficient altitude to reduce collective to minimize power applications and as such upon realizing despite instrument indications as stated the a/c was descending rapidly and would impact into a parking lot of vehicles below me." The pilot stated that there was no other suitable terrain to land on. A witness stated, "The pilot then nosed the helicopter over and started moving forward and gaining altitude. At that point I started to turn to the person next to me to say something but my attention was immediately drawn back to the departing helicopter because of a change in the sound from the helicopter." The engine was test run and it produced full rated power.

On July 14, 2001, about 2015 central daylight time, a Schweizer 269C helicopter, N61434, piloted by a commercial pilot, sustained substantial damage on impact with vehicles and terrain on takeoff near a parking lot near Walker, Minnesota, following a reported in-flight loss of engine power. The sight seeing flight was operating under 14 CFR Part 91. Visual meteorological conditions prevailed at the time of the accident. No flight plan was on file. The pilot and two passengers sustained minor injuries. The local flight was originating at the time of the accident.

The pilot stated:

Two individuals approached my staff and indicated a desire to enjoy a

ride. I completed my refueling operation of the a/c [aircraft] and

verified that I had indeed 18 gallons of 100LL fuel in the 300C's tanks.

I started the a/c as normal, completed a full runup procedure to include

mag[neto] checks and positioned the a/c for the pax [passenger] to board.

Upon securing them I asked if either of them had ridden in a helicopter

before and one stated that he had and the inboard pax stated he had not.

I reassured both that I will inform them of my intentions prior to all

maneuvers and that it is always my desire to provide a very smooth

controlled flight. I briefed my route of departure as being straight out

and slightly to the right after effective translational lift. I

verbalized that I was increasing power after all internal checks were

complied with via a standardized University of North Dakota approved

Schweizer 300c checklist that I've chosen for my use. I stated we would

be getting light on the skids and then once we were airborne, I stated we

are now flying, just like a butterfly. I then verbalized as I do on every

flight due to my military habit transfer, that flight controls and CG

[center of gravity] were both normal. I verified visually and verbally

then stated engine and rotors are 3200 rpm and we have power for takeoff

(another standardized procedure I used on every flight...) Manifold

pressure indicated 23-23.5' of MP [manifold pressure] (placard limits for

the given conditions were determined to be 26.2'). The fact that all was

indicating normal, I re-confirmed power settings and we departed via a

normal rate of climb takeoff. All indications were perfect up to a point

at which I was at approximately through ETL [effective translational lift]

(16-24 kts) @20-25 kts and at 15-20 ft AGL. At the time I normally

experience an increased efficiency and continued rate of ascent, the

opposite occurred. The aircraft became excessively sluggish, with

virtually no power. I immediately visually confirmed that the engine was

operating and that a complete engine loss was not experienced. The engine

and rotor RPM's were definitely joined and had remained within the green

arc. The manifold pressure was @ 24-24.5'. It was quite obvious very

quickly the aircraft had momentarily suffered a partial power loss. I was

not at sufficient altitude to reduce collective to minimize power

applications and as such upon realizing despite instrument indications as

stated the a/c was descending rapidly and would impact into a parking lot

of vehicles below me. I leveled the a/c slowed the forward airspeed and

applied all remaining collective in an effort to slow the main rotor

blades prior to impact. I struck the top of a vehicle in a level profile

slid off the left front side and the a/c then came to rest on its left

side. As the critical angle of the blades was reached the blades impacted

a vehicle in front and left of my route of flight and they stopped

instantly. I reached up and turned the key off and pulled the mixture and

turned off the battery while all three of us egressed out of the a/c with

the assistance of numerous people in the area.

One of my ground personnel staff, a 46 year old adult, stated to me he

had determined something different in the sound of the a/c on climb out.

He stated it was not a perceptive 'backfire' or complete loss of engine

noise, yet a subtle change of 'some type'. ...

The fact that I had personally executed the same type departure out of

that location for the previous days for @ 100-150 times during much

greater demanding atmospheric conditions during the high temp and high

humidity times of the previous afternoon and with similar loads makes me

very suspect as to the integrity of the engine and its performance. All

weight and balance calculations were within CG limits and the DA [density

altitude] of 2700 was as noted, not excessive. ...

The pilot stated that there was no other suitable terrain to land on.

A witness stated:

The helicopter lifted about 3 to 5 feet vertically off the platform and

hovered for several seconds. The pilot then nosed the helicopter over and

started moving forward and gaining altitude. At that point I started to

turn to the person next to me to say something but my attention was

immediately drawn back to the departing helicopter because of a change in

the sound from the helicopter. The first thing that I noticed was that

the helicopter was now flying level, still moving forward but not gaining

altitude. ...

The engine was shipped to Textron Lycoming for an engine run. The valves were inspected in accordance with Service Bulletin 388. The valve's readings were taken and found to be within specifications. On October 10, 2001, the engine was run in a test cell. The engine produced full rated power. (See appended engine test log.)

The Schweizer 269C Height Velocity Diagram at Sea Level figure was reviewed. The height, "15-20 ft", and velocity, "20-25" knots, the pilot stated in his statement were plotted. The intersection of the height and velocity was found in a crosshatched region on the figure. A note on the figure stated, "AVOID OPERATION IN CROSSHATCHED AREAS." (See appended helicopter manual excerpt.)