Loss of control

Circumstances:

The student was making his second solo flight. During the approach to land the student realised the helicopter was above the desired approach path. He elected to land on the grass surface a short distance beyond the helipad as he has been taught. The wind was blowing at 10 to 15 knots from the northeast, with the landing conducted in an east south east direction. The pilot said he began to enter the hover and turn the helicopter to the left, into wind. The aircraft continued the left turn, during which it began to move rearwards. The tail skid dug into the landing surface, resulting in the helicopter rolling to the left and striking the ground.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. Improper compensation for wind conditions.

2. Pilot encountered unforeseen circumstances beyond his capability.

3. Improper operation of primary flight controls.

The pilot was engaged in a local flight and was practising hovering at various altitudes. With the helicopter heading 320 degrees, the pilot commenced a slow descent from about 15 feet. The wind was 310 degrees at 10 knots gusting to 20 knots. While descending to about three feet, the helicopter began a slow yaw to the right through 30 degrees. The pilot elected to let the yaw continue and carry out a 360 degree pivot turn. After turning through about 100 degrees, the pilot stopped the descent by increasing power and pulling on collective. Coincidentally, the pilot reported that the helicopter then rapidly increased the rate of turn despite the application of full left anti-torque pedal. After about one turn, the pilot said he lost all control and following about another 3-4 turns, the helicopter crashed onto its left side at about 45 degrees angle of bank. During the sequence several mainrotor blade ground strikes occurred. The pilot said that he was also aware of overcontrolling on the cyclic control and pulling on collective at one stage in his efforts to control the helicopter. The investigation could not find any mechanical cause for the loss of control. Both the pilot and passenger reported that at no time did the passenger touch the controls or have his feet near the anti-torque pedals. Studies on helicopter tail rotor vortex rings indicate that these rings can form with a relative wind from 220 to 320 degrees at 10 to 25 knots, with further indications that the worst areas are around 250 and 290 degrees relative. In addition, the conditions suitable for the formation of a vortex ring are most favourable when the tail rotor is moving to the left, as in a right pedal turn. At the point where power was increased, the tail rotor was in a critical position with a relative wind from 250 degrees and strength from the left of between 10 and 20 knots. If the tail rotor was close to a vortex ring state, increased power would, through the torque effect, produce a marked right yaw. Due to the vortex ring, left pedal input would have no effect.

Following the completion of a flight in the local training area the aircraft was landed on Runway 36 at Roma. At the time the wind was north-westerly at five to eight knots and there was a thunderstorm to the south-west of the field. During the landing roll the wind velocity suddenly increased to about 25 knots. The aircraft swung to the left and ran off the side of the runway. The pilot was unable to regain directional control but shut down the engine before the aircraft ran into a ditch. This accident was not the subject of an on-site investigation.

The pilot made an early morning DEPARTURE from the station strip. He reported that as the aircraft accelerated past 65 to 70 knots he selected gear up, however, the gear did not immediately retract and the gear safety override warning activated. The gear then retracted but shortly afterwards he heard a "clanging" noise which he assumed was coming from the engine. He immediately reduced power, selected gear down and turned back towards the strip for a forced landing. The turn was commenced from about 150 to 200 feet above the terrain, but after turning through about 160 degrees the aircraft stalled. The aircraft collided with the ground and after a ground run of approximately 122 metres the left wing struck two trees which yawed it through 180 degrees. The gear collapsed and the aircraft skidded backwards for 32 metres. An examination of the aircraft failed to detect any pre-impact malfunction with the engine or propeller. The source of the "clanging" noise reported by the pilot could not be established, although the post impact damage may have destroyed the evidence of the noise source. There was no other evidence of power loss. The pilot had been working very long hours over the preceding three days and was fatigued. It is possible that the level of fatigue had a deleterious affect on the pilot's ability to rapidly and correctly assess the action required. The pilot mistakenly identified a noise from an unknown source as an engine or propeller malfunction and reduced power by a substantial amount. The pilot then selected gear down and attempted a turn back manoeuvre from only 150 to 200 feet above ground level without increasing power. The aircraft subsequently stalled. The activation of the gear safety override system probably added to the confusion and reinforced in the pilot's mind that the aircraft had a serious malfunction.

Circumstances:

The pilot reported that, very shortly after liftoff from Runway 15, he heard a loud bang. He was advised by one of the passengers that the baggage door, situated on the upper right side of the fuselage above the wing trailing edge, had opened. Apart from a high noise level, aircraft behaviour seemed unchanged. The pilot said that he recalled a section in the Pilot's Operating Handbook which stated that the flight characteristics of the aircraft would not be affected by an unlatched door in flight. He reassured the passengers to this effect. As the aircraft climbed through about 150 feet, with landing gear still extended and flap still at 15 degrees, the pilot reduced engine power to what he thought was about 1800 RPM and turned left to land on the eastern section of Runway 06. He had assessed there was insufficient length of Runway 15 remaining to land straight ahead. As the aircraft turned with 15-20 degrees angle of bank, it was seen to adopt a nose-low/left-wing-low attitude and impact the runway. The pilot reported that the aircraft was in a nose low attitude and close to the ground when it rolled left. He applied right aileron and full power but was unable to prevent the left wing striking the runway surface. The initial impact was 83 metres left of the Runway 15 centreline on a heading of approximately 090 degrees magnetic. The left wing tip contacted the ground first followed by the nose. The aircraft skidded 51 metres before coming to rest. The landing gear collapsed during the impact sequence. Neither the pilot nor any of the passengers reported hearing the stall warning operate prior to impact. The surface wind at the time of the accident was estimated to have been from the south-east at 10 15 knots. There was no significant turbulence. On inspecting the aircraft, the baggage door was still attached to the airframe via its two hinges. The hold-open stay was broken. No fault was found with the door locking mechanism, either through the external locking handle, or the internal lever. The royalite plastic lining, including the protective cover for the internal lever, and insulation material had been torn from the inner face of the door and were found adjacent to the runway. The internal locking knob was securely stowed in the locked position. The pilot reported that it was his habit to check the door as he stepped on to the wing to enter the cockpit. As far as he could recall, the door was locked prior to the flight. Photographs taken of the aircraft shortly after the accident appear to show the external locking handle in the stowed position. However, it is possible for the handle to be stowed and the locking pins to be located outside the fuselage skin, thus leaving the door unlocked. Because of accident damage, the operation of the stall warning system could not be tested. The pilot could not recall the speed of the aircraft during the turn. It seems probable, in view of the aircraft configuration and the engine power setting, that the airspeed was closer to, rather than substantially higher than, the basic stalling speed of the aircraft. The luggage door is positioned on the upper right side of the fuselage above the wing trailing edge. It is hinged on the top of the fuselage with the hinge line parallel to the aircraft centreline. With the door open, the airflow pattern over the rudder/tailplane could be altered. There is no reference in the Aircraft Flight Manual or the Pilot's Operating Handbook to operations with the baggage door open. However, there is reference in the Operating Handbook to the actions to be taken in the event of the cabin door becoming unlatched in flight (flight characteristics unaffected). It was this that the pilot recalled at the time of the occurrence and which led him to reassure his passengers that there was no cause for concern. This knowledge could also have influenced his decision to turn left and land on the remaining section of the other runway.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. The pilot probably did not adequately check the security of the baggage door before flight.

2. The baggage door opened as the aircraft took off.

3. In the subsequent landing, for reason(s) which could not be established positively, the pilot was unable to prevent the left wing from contacting the ground.

Recommendations:

There have been a number of accidents to M-20 aircraft involving in-flight opening of the baggage door. In at least two cases overseas, the accidents were fatal and involved loss of control at low speed. In a non-fatal accident overseas, airspeed and vertical speed indications became erratic after the baggage door came open and contributed to the pilot stalling the aircraft. In Queensland in 1984, in circumstances strikingly similar to the accident under discussion here, the pilot of an M-20 aircraft was attempting a landing after the baggage door opened shortly on take-off. He reported that the aircraft "fell away" as it crossed the end of the runway. The aircraft struck the runway surface right wing first, sustaining substantial damage. The pilot did not hear the stall warning sound. These examples indicate that the influence of an open baggage door on the flight characteristics of the Mooney 20 could be significant. Following the first fatal accident, a Service Bulletin dated 28 September 1988 was issued by Mooney Aircraft Corporation (SBM20-239) applying to various serial numbers of M20J Models to prevent in-flight opening of the baggage door. The Bulletin contained instructions to modify the inside latch on the baggage door and was incorporated in Australian Civil Aviation Authority Airworthiness Directive AD/M20/44 dated 23 February 1989. The baggage door inside latch was not a factor in this accident. However, that such modification action to the latch was considered necessary to prevent in-flight opening of the door raises a number of other aspects. These include:

1. Whether any warning device (such as a warning light in the cockpit) is necessary to alert the pilot that the door is not locked.

2. Whether any special technique is required during approach and landing to ensure safe control of the aircraft with the baggage door open.

3. Whether any warning should be included in the Aircraft Flight Manual about possible control problems in the event of the baggage door opening during flight.

4. Whether any flight test program is necessary to determine the handling characteristics of the aircraft with the baggage door open. It is recommended that the Civil Aviation Authority examine the above aspects with a view to ensuring the maximum safety level for Mooney 20 operations consistent with practicable economic considerations.

Because of deteriorating lift conditions, the pilot elected to make an outlanding. The paddock selected had been recently ploughed and the surface was soft. Almost immediately after touchdown the glider yawed, then groundlooped through 90 degrees, resulting in a compression fracture of the fuselage. It was likely that the glider had been affected by a sudden wind gust shortly after touchdown, and the pilot had been unable to maintain directional control.

The pilot was making a landing approach in moderate crosswind conditions. Touch-down was made in a three-point attitude at an airspeed of about 40 knots. Immediately afterwards, the pilot experienced difficulty in preventing the into-wind wing from rising. He elected to go around and applied full throttle, but was unable to maintain directional control. The propeller struck the ground and the aircraft cartwheeled before coming to rest. Recorded aerodrome information received by the pilot indicated that the surface wind was gusting above the aircraft maximum demonstrated crosswind component. On final approach, the pilot became aware that a significant crosswind existed, but he continued the approach, using a short field landing technique. When directional control was lost after touchdown and a go around was attempted, the combination of an uncontrolled turn downwind, the low airspeed and a gusty wind caused the aircraft to stall.

Circumstances:

The helicopter was operating onto a floating pontoon situated adjacent to a reef area. The pontoon was 30.65 m long and 9.32 m wide and consisted of a wooden platform mounted above two steel floats. A series of hardwood joists 295 mm x 85 mm and approx. 950 mm apart were mounted between the floats and 35 mm x 110 mm hardwood decking was nailed to the joists to form the platform surface. The decking ran lengthwise along the pontoon. The pontoon was constructed in 1985 and had been in operation almost continuously since then. While mainly skid equipped helicopters operated onto the pontoon, it had also been used by wheeled helicopters, including the Agusta 109. It was established that Agusta 109s had landed on the pontoon on some hundreds of occasions prior to the accident. Company pilots reported that they had observed decking planks bend when subjected to the weight of the Agusta 109 through its mainwheels. For this reason, the general practice for Agusta 109 operations onto the platform was for the mainwheels to be positioned over the joists when landing along the pontoon parallel to the decking. At the time of the accident, there was a northerly wind at about 15 kts and the pontoon was pitching some 25-30 cm in the swell. The northern end of the pontoon was occupied by another company helicopter which had just landed and was parked across the pontoon with its engine running and passengers still on board. VH-LHJ approached into wind to land along the pontoon. The helicopter was being flown by the pilot in the left seat. Shortly before the wheels contacted the decking, the pilot in the right seat opened his door to check the position of the mainwheels in relation to the joists. As the mainwheels touched the surface, he reported to the pilot flying the aircraft that the mainwheels were 6-8 in behind the beam. As the weight of the helicopter was transferred to the wheels, the right-seat pilot saw the decking beneath the right mainwheel flex slightly and then crack and break. The helicopter rolled rapidly to the right and the main rotor blades began impacting the pontoon and the water. The helicopter eventually came to rest on its right side, having veered about 130` to the right adjacent to the southern edge of the pontoon. The impact forces destroyed the main rotor blades, substantially damaged the rotor head, and broke the tail boom. There was no evidence of any fault in the helicopter which might have contributed to the accident. There was also no evidence of a hard landing or any other pilot-related aspect which might have caused excessive loads to be placed on the decking during the landing sequence. The investigation therefore focused on the pontoon itself, and a study was commissioned to examine the strength of the pontoon decking with respect to the helicopter types known to use the pontoon. The results of the evaluation of the pontoon decking were as follows 1. The condition of the decking timber was such that deterioration due to exposure to the elements was concluded not to have been a factor in the deck failure. 2. The failure of the decking when subjected to Agusta mainwheel loading was due to grossly excessive bending stress. The overload factor was calculated as 8.39 and readily explained the failure. The only pontoon design documentation which could be located concerned the general structure and dimensions of the pontoon and contained no details on deck strength considerations. No comment can be made, therefore, as to whether the wheel or skid loadings of the various helicopter types using the pontoon, and particularly those for the Agusta 109, were considered during the design of the pontoon.

Significant Factors:

The following factors were considered relevant to the development of the accident

1. The strength of the pontoon decking was inadequate for Agusta 109 operations.

2. The pontoon decking failed due to excessive bending stress when subjected to loading through the right mainwheel of the helicopter.

Recommendations:

The helicopter operator and the pontoon owner, along with the Civil Aviation Authority (CAA), were notified of the progress of the investigation. This included information contained in a preliminary report followed later by the complete testing details, technical analysis, and stress calculations concerning the pontoon decking. The analysis concluded that the strength of the decking was inadequate for all helicopter types which used the pontoon and steps were instituted by the operator and the pontoon owner for the deck to be strengthened.

1. A recommendation was made to the CAA on 13 September 1991 that the circumstances of the accident be brought to the attention of other organisations involved in operations on to helicopter landing sites with timber decking and that these organisations confirm the design specifications of those surfaces for the particular types of helicopter involved.

2. It is further recommended that the Civil Aviation Authority through surveillance, following the failure and subsequent repair of this pontoon, confirm that the pontoons and other helicopter landing sites which are being used by this operator, have the structural integrity to accommodate operations of the relevant helicopter types.

Circumstances:

The aircraft had taken off on runway 24 towards a range of hills. Wind at the time was reported as a steady 20 knots from the south-west, straight down the runway. After take-off, the pilot retracted the landing gear and reduced power for climb. He reported that soon after, the aircraft encountered a windshear, lost airspeed, and failed to climb. He did not reapply full power. There were no clear areas ahead, so he commenced a left turn; however, the airspeed decayed further, and the left wing dropped. The aircraft struck the top branches of a 15 m pine tree, rolling inverted before coming to rest approximately 15 m from a house. The occupants were trapped in the wreckage until emergency services arrived. The accident site was approximately 1 250 m south-west of the end of the runway. The terrain is below a five percent gradient, but beyond this area it rises quite steeply to a ridge line approximately 5 km from the runway. No fault was found with the aircraft. There was evidence from propeller strike marks on severed branches that the engine had been delivering substantial power at the time of impact. The area is well known for local wind effects due to the terrain. The prevailing wind direction would have been conducive to wind shear in the lee of the ridge where the accident occurred. This is the second of three similar accidents which have occurred within an area of 1.5 km during the last few years. In each case the aircraft failed to outclimb the terrain after taking off from runway 24.

Significant Factors:

The following factors were considered relevant to the development of the accident:

1. The aircraft may have encountered windshear soon after lift-off.

2. The pilot did not operate the aircraft for maximum performance.

3. The pilot was not able to maintain speed.

Recommendations:

Over the past ten years BASI records indicate at least 16 take-off accidents to fixed wing aircraft attributed in part or totally to the effects of wind over the local terrain and to high density altitude. The following recommendations are made:

1. The CAA consider preparing an educational article to be widely distributed detailing considerations for GA type aircraft operations in areas where flight may be affected by terrain, wind, and density altitude.

2. The CAA bring to the attention of training schools the need to accent these issues in both theoretical and practical training.

Spraying operations were being conducted in generally calm weather conditions. One load had been sprayed successfully, but the pilot later advised that, as he manoeuvred at the end of the second run with the next load, sink was encountered. Although he dumped the remainder of the load, he reported that he had insufficient time to increase power. The aircraft collided with a tree, then struck the edge of a road and groundlooped into an adjacent crop. Weather conditions at the time were unlikely to have produced any sink. It was probable that while turning towards rising ground the pilot misjudged the slope of the terrain. The aircraft had stalled, with insufficient height available in which to effect a recovery.