Andover, NJ, USA
N6147L
Schweizer 269C-1
The student pilot (SP) & flight instructor (FI) were practicing autorotations with a power recovery in a Schweitzer 269C-1. The helicopter struck the runway hard, collapsed the left skid and rolled over on its left side. The SP reported that the main rotor rpm was increasing and he tried to raise the collective. It did not move, and when it did move, it came all the way up, the main rotor blades stalled, and the helicopter hit hard. The FI said the SP raised the collective, and he immediately lowered it, added power, and was unable to prevent a hard landing. The FI reported that the engine responded to his inputs. A check of the flight controls found that the collective and main rotor swash plate operated free and easy, with no evidence of jamming or resistance. An engineering test pilot with Schweitzer reported a momentary pop-up of the collective to full up and back down in less than 1 second would not cause blade stall. Blade stall would require the collective to be held full up for 3 or more seconds. The FI reported that his hand was near the collective, but not on it. No loose items were found in the helicopter that could have restricted movement of the collective.
HISTORY OF FLIGHT On August 21, 2002, about 0948 eastern daylight time, a Schweizer 269C-1, N6147L, was substantially damaged, when it landed hard during a practice autorotation at Aeroflex-Andover Airport (12N), Andover, New Jersey. The certificated flight instructor and student pilot received serious injuries. Visual meteorological conditions prevailed for the instructional flight that originated from Essex County Airport (CDW), Fairfield, New Jersey. No flight plan had been filed for the flight that was conducted under 14 CFR Part 91. According to the flight instructor: "...Upon arrival at 12N, 3 normal approaches to the runway 3 were conducted...[the student pilot] was advised that the next approach would a be power recover autorotation...[the student pilot] was advised that he was to enter the maneuver at 1,200 feet AGL, and at 2,900 [engine] rpm, and 65 mph....[the student pilot] entered correctly then at about 700 feet MSL [117 feet AGL], he applied full up collective. I immediately applied full throttle and aggressively lowered the collective. I also applied slight aft cyclic in an attempt to regain rotor rpm. There was insufficient altitude to regain rotor rpm and in spite of the flare just before contact, the helicopter hit the runway at a high rate of descent sufficient to cause the helicopter to end up on its left side...." The student pilot reported: "...After the normal approach, a high final auto rotation from approx 1,000 feet was conducted in the following manner: >The throttle was closed and held in the detent position to initiate the autorotation. >Simultaneously the collective was lowered to its lowest position to permit the auto rotation. >During the autorotation, the rotor rpm was increasing towards its limit and therefore an attempt was made to slowly raise the collective to maintain the rotor rpm below the limit. >Several attempts were made to slowly raise the collective to no avail until a final attempt at which time the collective traveled its full distance and caused the rotor blades to slow up to a point where they became ineffective. >Shortly after this, the helicopter landed on the aft landing skids and rolled. Prior to the landing...[the flight instructor] stated, 'Not this mechanical problem again." One witness who was in the refueling area, about 1,300 feet from the accident site stated: "...I observed the helicopter on its third final approach. On short final, I observed the lack of engine noise. At approximately 100 ft, the aircraft descended rapidly impacting the end of runway 03. Upon impact the helicopter rolled onto its left side...." Another witness was waiting in an airplane on the taxiway, adjacent to the approach end of runway 03. He reported that the helicopter appeared to drop in from about 100 feet. It hit tail first, then on the left skid. It slid and rolled over onto its left side.. The accident occurred during the hours of daylight at 41 degrees 0.36 minutes north latitude, and 74 degrees, 44.36 minutes west longitude. PERSONNEL INFORMATION The flight instructor held an airline transport pilot certificate with ratings for airplane multi-engine land, and a commercial pilot certificate with ratings for airplane single engine land and rotorcraft-helicopter. In addition, he held a flight instructor certificate with airplane single and multi-engine airplane ratings, instrument airplane rating, and rotorcraft-helicopter ratings. He was last issued a Federal Aviation Administration (FAA) second class airman medical certificate on June 22, 2002. The flight instructor reported his total flight experience as 11,700 hours, with 711 hours in rotorcraft, and 250 hours in make and model. In addition, he had logged 22 hours in make and model within the preceding 90 days. The second pilot held a student pilot certificate/FAA airman medical certificate, issued on July 22, 2002. The student pilot had not soloed. The student pilot reported his total flight experience as 42 hours, with 22 hours in make and model, all accumulated within the preceding 90 days. AIRCRAFT INFORMATION The helicopter was maintained in accordance with the manufacturer's inspection program. The last 12-month (annual) inspection had been completed on February 27, 2002. Examination of the inspection form from Schweizer revealed that the 12-month inspection was also called an annual inspection. The student pilot was considering purchase of the helicopter, and had requested a pre-purchase inspection of the helicopter. According to the letter from the company the conducted the inspection, several comments were made about the condition of the helicopter. Examination of the maintenance records revealed that the helicopter had experienced a hard landing, and been returned to service following the event. Included were the comments about the hard landing inspection, and the replacement of both the "forward and aft cross beams." A list of airworthiness directives (AD) that had been complied with was found in the maintenance records. Schweizer Aircraft Corporation was contacted and the list compared to the list that they maintained. All ADs were found to be complied with except for 2000-16-05, which called for an inspection of the tail rotor swash plate and pitch link control rods. A list of service bulletins (SB) was found in the maintenance records. Schweizer Aircraft Corporation was contacted and the list compared to the list they maintained. Service bulletins through C1B-010 had been complied with. Additional service bulletins issued by Schweizer Aircraft Corporation, not listed in the maintenance records were C1B-11, not applicable by engine serial number; C1B-012, not applicable, by helicopter serial number; C1B-013, not applicable by helicopter serial number; and C1B-014, issued on August 9, 2002. This service bulletin called for a one time detailed inspected of the support shaft between the main rotor drive shaft and tail rotor drive shaft boom. METEOROLOGICAL INFORMATION A witness reported the sky was clear, and there was a variable wind from the north at 5 knots. The closest recorded weather was at Essex County Airport (CDW), Fairfield, New Jersey, 22 nautical miles distant, on a magnetic heading of 125 degrees. The 0953 weather observation from CDW, included: sky clear, and variable wind at 6 knots. Visibility was recorded as 10 statute miles. AIRPORT INFORMATION . Aeroflex-Andover was an uncontrolled airport with a 1,981-foot-long runway that was 50 feet wide. The approach to runway 03 was over water with about 100 feet of land preceding the end of the runway. The taxiway was located on the west side of the runway. WRECKAGE AND IMPACT INFORMATION The accident occurred on the left side of the approach end of runway 03, where the taxiway connected to the runway. The first point of ground contact occurred on asphalt, and consisted of a red paint transfer, a gouge in the asphalt, and an oil stained area. The only red paint observed on the helicopter was on the tail rotor blades. The next ground contact point was 20 feet beyond the initial ground contact, parallel to the left edge of the runway, where there were numerous gouges and white paint transfer marks on the asphalt. The helicopter was located 63 feet from the initial ground impact mark, lying on its left side, on a heading of 170 degrees. The bubble canopy was shattered. The mixture was full rich, the throttle was full open, the fuel shut off valve was open, and the collective was full down. Nothing was observed in the cockpit that would have impeded the movement of any of the flight controls. One tail rotor blade was bent 90 degrees, opposite the direction of rotation, near the hub. The other blade was not bent. Both blades had leading edge impact damage near the tip. The blue main rotor blade was bent about 18 inches outboard of the blade grip and folded down about 135 degrees from the plane of rotation. The outboard 4 feet of the blade was bent up about 30 degrees from the plane of rotation, and chordwise scrape marks were visible on the bottom of the outboard 8 inches of the blade. The red blade, next in rotation, was bent down about 30 degrees from the plane of rotation, outboard of the blade grip. The white blade, next in rotation, was not bent down. However, the piston for the lead-lag damper was pulled out of the case and remained attached to the trailing edge of the blade. The drive belts between the transmission and engine were intact and detached from their pulleys. The drive shaft to the tail rotor was separated at the aft side of the pulleys to the main transmission. The brace between the main rotor mast, and the tail boom was intact and secured at both attach points. The housing over the tail rotor drive shaft was separated at the point where the fuselage braces attached to the tail boom. Longitudinal scrape marks were visible on the underside of the fuselage and engine. The oil quick-drain on the bottom of the engine sump was found imbedded in the asphalt along the debris trail. The carburetor was separated from the engine sump; however, the engine control cables to the carburetor were attached. The tail boom was separated about 1/3 of the distance between the fuselage, and the tail rotor. However, the pushrod that connected the rudder pedals to the tail rotor was intact. Movement of the anti-torque pedals in either direction brought about a corresponding movement on the tail rotor pitch link control rods, and changed the pitch of the tail rotor blades. The cyclic was exercised through its full range of motion. There was no binding as the cyclic moved in the corners of movement. The connection to the main rotor swash plate was secure, and all movement of the cyclic brought about a corresponding movement of the swash plate, and the main rotor pitch link control rods. When the collective was lifted to the full up position, a corresponding movement on the swash plate, and main rotor pitch link control rods was observed. The collective was moved through its full range of motion several times, with no binding or resistance felt. All main rotor and tail rotor pitch link control rods were intact. ADDITIONAL INFORMATION In a follow-up interview, the flight instructor was asked if there was anything in the cockpit that could have impeded the movement of the collective, and he reported there was nothing. He reported that his left hand was near, but not on the collective, and that as soon as it was moved up, he pushed it full down. According to an engineering test pilot from Schweizer Aircraft Company, Schweizer Aircraft uses main rotor rpm rather than percent of maximum rpm for measuring main rotor speed (Nr) on the Schweizer 269C-1. The green arc for operation is 504 rpm (100 percent), to 390 rpm (77.4 percent). He also reported that if the blades were not stalled, that recovery of Nr would be synonymous with lowering of the collective. However, if the blades had been stalled, and Nr had been allowed to decrease below 380 rpm (75.4 percent), recovery of Nr, sufficient to conduct a successful autorotation would be dependent upon the minimum Nr reached, and altitude of the helicopter above the ground. The engineering test pilot also reported that when Nr was in the upper portion of the green arc, to achieve a blade stall would require movement of the collective to the full up or near full up position, and have it held there for at least 3 seconds or longer. The main rotor blades would not stall with a pop up of the collective to the full up position for less than 1 second, followed by an immediate return to the full down position No items were retained, and the there was no one available to accept custody of the helicopter when the Safety Board investigator was ready to leave the accident site. The operator took custody of the helicopter a few days later and then turned it over to the insurance adjustor.
The flight instructor's delayed remedial action to correct the low rotor condition. A factor was the student pilot's improper use of the collective, which created the low rotor condition.
Source: NTSB Aviation Accident Database
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