R44 crash with pics
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Just a thought (and don't shoot me down, I only drive planks!), but if going in the drink (or onto any abnormal landing surface), I was always taught to 'crack the door' open... Is it possible that the pilot has done this and the door just so happens to have swung wide open because of the low nose attitude and low forward airspeed?
From the sequence of pics I'd hazard a guess that he was yawing hard throughout which suggests a lack of t/r authority. At one stage he was at a pretty extreme nose down angle which reduced dramatically as he neared the water. The coning angle and blade pitch in the pic just before impact both look considerable suggesting low Nr which might fit with poor yaw control.
Hypothesis?
Inadvertent or premature rapid lift off (hence door still open) probably with insufficient Nr and/or power, subsequent loss of yaw control perhaps due to unpreparedness and Nr droop; he managed to correct heavy pitch down to very nearly level upon impact and after almost 180deg of yaw. (Does a Robbo pitch down if you drop the lever abruptly??? A surprised pilot in that situation would almost certainly drop the lever to contain the climb and input nose down by reflex and could easily overdo that) Realised it was unrecoverable, did best to correct pitch, hauled collective full up to cushion arrival. Lower fuselage took impact with Nr now so low that there was insufficient energy in the rotor to disrupt it.
Lucky people.
Hypothesis?
Inadvertent or premature rapid lift off (hence door still open) probably with insufficient Nr and/or power, subsequent loss of yaw control perhaps due to unpreparedness and Nr droop; he managed to correct heavy pitch down to very nearly level upon impact and after almost 180deg of yaw. (Does a Robbo pitch down if you drop the lever abruptly??? A surprised pilot in that situation would almost certainly drop the lever to contain the climb and input nose down by reflex and could easily overdo that) Realised it was unrecoverable, did best to correct pitch, hauled collective full up to cushion arrival. Lower fuselage took impact with Nr now so low that there was insufficient energy in the rotor to disrupt it.
Lucky people.
Last edited by Wageslave; 15th Jun 2012 at 08:51.
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They all shake a fair bit when the cyclic is moved to allow the swash plate to be at its limit of travel, depending upon how well rigged they are.
Maybe he could just have allowed the cyclic right forward and didn't twigg why it was vibrating like crazy?
Maybe he could just have allowed the cyclic right forward and didn't twigg why it was vibrating like crazy?
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Don't mean to start a yes-no fight here, we are just all here to learn.
I've talked this weekend to two direct colleages of the pic, and it turned out that resonance in some form WAS involved and that that this was the incentive for the pilot to pull the collective despite being on only 70%. The partly wooden construction of the landingspot is also thought to have worsen things.
IAgain, perhaps something can be learned.
I've talked this weekend to two direct colleages of the pic, and it turned out that resonance in some form WAS involved and that that this was the incentive for the pilot to pull the collective despite being on only 70%. The partly wooden construction of the landingspot is also thought to have worsen things.
IAgain, perhaps something can be learned.
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As an addition, in time there will be a report on the matter by the Dutch Authorities on www.onderzoeksraad.nl. If it comes (could take a few months or more) I will let you know and translate the most important conclusions...
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I am sure that you are not starting a fight.
I think though that it should not be "resonance" as we understand the term. Resonance requires that the blades shift so that the rotor becomes unbalanced - like a washing machine trying to spin with an unweighted load. The design of the R44 rotor head precludes that unless it is significantly broken or FOD is picked up in the rotor and then lifting-off would be exactly the wrong reaction.
I can accept that vibration led the pilot to conclude that he had to lift. I can accept that the wooden structure may have played a part in leading him to that decision.
I think though that it should not be "resonance" as we understand the term. Resonance requires that the blades shift so that the rotor becomes unbalanced - like a washing machine trying to spin with an unweighted load. The design of the R44 rotor head precludes that unless it is significantly broken or FOD is picked up in the rotor and then lifting-off would be exactly the wrong reaction.
I can accept that vibration led the pilot to conclude that he had to lift. I can accept that the wooden structure may have played a part in leading him to that decision.
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No not resonance as we understand it, cyclic jammed right forward, machine vibrating, such vibration being added to perhaps by a non rigid platform, inexperienced or ill equipped driver, collective jerked up at 80%, yea all resonating nicely enough to rest my case I think.
80% stall demonstration
hmmm....
that may well be the case that you train that way, but it is also a wilful violation of the limitations section of the AFM. There is a minimum rotor speed for power on, and you will find that RHC and the FAA would be kind of interested in the procedure.
Having said that, the R-22/44 and full articulated heads are the only ones that you will not cause massive root bending loads. Don't try the same thing on a B206 either.
If you need to operate outside the certified envelope, then you need to do what we do, and be in experimental category, as you are in breach of the law.
that may well be the case that you train that way, but it is also a wilful violation of the limitations section of the AFM. There is a minimum rotor speed for power on, and you will find that RHC and the FAA would be kind of interested in the procedure.
Having said that, the R-22/44 and full articulated heads are the only ones that you will not cause massive root bending loads. Don't try the same thing on a B206 either.
If you need to operate outside the certified envelope, then you need to do what we do, and be in experimental category, as you are in breach of the law.
Last edited by fdr; 9th Jul 2012 at 08:19.
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80% stall demonstration
Surely there is more rigidity with power on than power off so I can't see what is wrong with Gordy's excercise as he describes it. It's not one I do, except perhaps approaching the loss of authority when a hovering auto is done, but that's power off.
Can't say the T/R in the 22/44 demonstrates a loss of authority during a hovering auto, perhaps we could do them in a crosswind from the right to help the effect?
One thing I point out in all hover autos is the RRPM that the M/R blades actually stall and then allow the aircraft to fall.
Cheers tet
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Report
Hi, This week an official investiagion report was published regarding this incident.
The report is to be found here: http://www.onderzoeksraad.nl/docs/ra...029_PH-WQW.pdf
The report is however in Dutch, so for the people interested it would be nice to use Google Translate on it. I will post some findings out of the report perhaps later this week if I find some time to do it.
The report is to be found here: http://www.onderzoeksraad.nl/docs/ra...029_PH-WQW.pdf
The report is however in Dutch, so for the people interested it would be nice to use Google Translate on it. I will post some findings out of the report perhaps later this week if I find some time to do it.
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Not one for wild speculation but pictures suggest to me getting airbourne without hydraulics. Trying to hover then leads to overcontrolling and the lag is so great that extreme attitudes can result. Possible scenario would be an unplanned lift off or having lifted with the door open, the pilot's attempt to grab the door with his left hand could have knocked off the hydraulic switch. Will be interested to see report.
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wow look at the pics in the pdf accident report. Ive never seen an R44 with that much front cyclic during warm up. That much aft and he would have cut his tail...
I think many factors came together here. For sure the pilot was super nervous and in a hurry. The Map in full size on his knees. Door not closed, friends watching him takin of...
I think many factors came together here. For sure the pilot was super nervous and in a hurry. The Map in full size on his knees. Door not closed, friends watching him takin of...
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A few quick notes from the conclusion of the report:
- There have been no clues for any technical failures on the helicopter.
- The platform was lacking some maintenance, however it is thought that this did not contribute to the accident
- It is thought that the pilot during the startup had pushed the cyclic in a too much forward position and was not aware of this
- This led to more than normal virbration and shaking of the helicopter and as a result the pilot started to look for the 'neutral position' of the cyclic (perhaps in the wrong way the investigators speculate).
- While looking for the 'neutral position (is that a good translation?) it is possible that that collective was not fully in the downward position
- During this proces the rotor rmp increased, with as a result a decrease in drag between the helicopter and the platform, resulting in a turning of the helicopter.
- The investigators seem to think that the pilot did not adequatly react on this situation.
- While having a low rmp (70 to 80 %) the pilot decided to pull the collective, being affraid he would fall in as a result of the vibration and turning of the helicopter.
- This resulted in a loss of control
- It is not known if and what the influence of the cyclic friction was since the friction was unfortunately not directly looked at after recovering the helicopter
- There have been no clues for any technical failures on the helicopter.
- The platform was lacking some maintenance, however it is thought that this did not contribute to the accident
- It is thought that the pilot during the startup had pushed the cyclic in a too much forward position and was not aware of this
- This led to more than normal virbration and shaking of the helicopter and as a result the pilot started to look for the 'neutral position' of the cyclic (perhaps in the wrong way the investigators speculate).
- While looking for the 'neutral position (is that a good translation?) it is possible that that collective was not fully in the downward position
- During this proces the rotor rmp increased, with as a result a decrease in drag between the helicopter and the platform, resulting in a turning of the helicopter.
- The investigators seem to think that the pilot did not adequatly react on this situation.
- While having a low rmp (70 to 80 %) the pilot decided to pull the collective, being affraid he would fall in as a result of the vibration and turning of the helicopter.
- This resulted in a loss of control
- It is not known if and what the influence of the cyclic friction was since the friction was unfortunately not directly looked at after recovering the helicopter
Last edited by Helicheese; 28th Mar 2013 at 12:52.
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Google translation
Original: http://www.onderzoeksraad.nl/docs/ra...029_PH-WQW.pdf
1
DOWN PAID DURING START
In the Netherlands, it ensures the risk of accidents and incidents as much as possible
limit. When it (almost) goes wrong, can be prevented by repetition, regardless of the
guilt, properly investigate the cause. It is then important for the investigation
independent of the parties takes place. The Safety Board chooses
therefore his own investigations and taking into account the dependency of citizens
compared to governments and businesses. The Council has in some cases required by law
research.
GENERAL INFORMATION
Occurrence: 2012029
Classification: Accident
Date and time1: March 25, 2012, around 14:30
Place of incident: Near Zwolle
Aircraft registration: PH-WQW
Aircraft Type: Robinson R44
Type of aircraft: Helicopter
Type of flight: Passenger Flight
Phase of flight: Start
Damage to aircraft: Significantly
Number of crew: A
Number of passengers: Two
Injuries: None
Other damage: None
Lighting conditions: Daylight
SUMMARY
The pilot of the helicopter with registration PH-WQW had the intention to make a flight with
passengers of Lelystad Airport (EHLE) to a helipad near Zwolle and back. During
starting the helicopter for the flight back to Lelystad, the helicopter began to shake
and to bounce and move the helipad. The driver tried the helicopter
to stand out from the platform, but a low rotor speed unit could not
maintain height. The helicopter came next to the helipad in a puddle right where
it just floated. The occupants were uninjured left the helicopter and to the side
swimming. The helicopter later sank to the bottom of the pond, and was the following day
salvaged. The unit became significantly damaged.
1 All times in this report are local unless otherwise stated.
2
FACTUAL INFORMATION
The flight and the accident
On the day of the accident, the pilot flew the PH-WQW along with two passengers
Lelystad Airport to a hotel with a restaurant, situated on a lake, near Zwolle. Directly
adjacent to the pond is a helipad. The flight from Lelystad to the
destination and landing on the helipad went without problems. The pilot flew
the platform in a northwesterly direction (against the wind), carried above the platform
rotation and put the helicopter then the platform, with the nose in eastern
direction, the direction of more than 100 meters terrace. The pilot and passengers spent
about an hour on the terrace by which they had a view on the helicopter. According to the pilot
He has all that time no one at the helicopter copper seen and no details were observed.
After the pilot had the passenger boarding the flight to Lelystad, he performed
a "walkaround" inspection. This was less extensive than the first flight because
though the pilot had flown the helicopter and then no one had seen the device. The
driver was right and the passengers were left to rear left. The pilot stated that he
when starting the checklist had followed the pedals were neutral and that cyclic2 and
collective3 friction were selected. Due to the sunny weather was the right door open to
prevent the temperature in the cockpit too high up. Then, with the
right door open, the engine started. The pilot stated that he intended the door
shortly before departure to close and open the door has not affected him further. The throttle
stood up after the start-up of the motor in the stationary state, after which the coupling of the motor
the rotor was turned. The rotor began to turn and the driver suggested by the
throttle the engine speed to about 60%.
When the link was successful was the pilot, according to his statement, continue the finishing
of the checklist including the reduction of the friction of the cyclic and of the collective. From
that time, the helicopter began to shake and to the left on the helipad.
According to the pilot felt the shaking same as when the rotor rotates and the cyclic
not 'neutral' state. The driver responded by using the cyclic to search for the "neutral point".
This had no effect, it was shaking violently and the helicopter began from one skid on the
other to bounce and further to the left with a slow twisting motion to the left.
The passenger sitting next to the driver was said that the rotor blades at that time less
spinning around than at the departure in Lelystad. The helicopter finally turned around 270
degrees counterclockwise and moved to the edge of the helipad.
To prevent the helicopter from the platform would fall, the driver pulled the collective
up for the purpose of the helicopter independently of the platform to come. The pilot stated that
it away from the edge and wanted to move back slightly. After the collective was up
drawn, the helicopter began to climb and a turn to the left to make. During this
began to maneuver the helicopter an up and down motion in order to make the transverse axis. Then
dropped the phone. The pilot stated that he had pulled up on the collective
when the helicopter hit the water. The pilot can not remember the hit, but
his feeling was not hard. The unit was initially on the right in the
water float. All occupants climbed through the left side of the helicopter and swam to the
side where they were picked up by bystanders. The pilot left the helicopter last.
Everyone remained unharmed. The helicopter then sank to the bottom of the pond, and was
a day later salvaged. The unit became significantly damaged.
2 The cyclic is the control organ with which the movement in the horizontal plane is controlled. The cyclic is
equipped with an adjustable friction (resistance) to prevent accidental movement.
3, the collective is the control organ with which the movement in the vertical plane is controlled. The collective is
equipped with an adjustable friction (resistance) to prevent accidental movement.
3
Figures 1 and 2: the PH-WQW shortly before it hits the water (source: M. Westveer)
The aircraft
The Robinson R44 is a four-seater helicopter powered by a piston. The chassis
consists of two metal beams, called skids.
The driver
The driver was in possession of a valid license for private pilot on
helicopters. He was also in possession of a type rating for the Robinson R44.
Number of hours in total 173
Number of hours by type 173
Number of hours during last three months 4
Table 1: Experience driver PH-WQW
Weather
According to data from the Royal Dutch Meteorological Institute (KNMI), the wind
near Zwolle during the accident from a northwesterly to northerly direction (330-360 degrees)
with a speed of 6 knots with gusts of 10 to 12 knots. The temperature was 13
degrees Celsius and visibility over 10 km.
The helipad
The helipad consisted of a metal structure which hardwood planks were
screwed. The platform has been for more than 50% surrounded by the water of the pond.
Figure 3: the helipad (source: Google Earth)
4
After the accident were warped boards found whose confirmation was partly
disconnected. Also had the support of the steel structure at some points subsided. On the
platform slide tracks were found.
Figure 4: partially loose board Figure 5: slide rails
For the helipad was called Airport Regulations issued by the county
Overijssel which meant that the platform could be used for performing takeoffs and
landings with helicopters. The Inspectorate for Environment and Transport (ILT) is responsible for monitoring
on the establishment, equipment and the safe use of the helicopter airport. The last inspection
was by IVW (the predecessor of the ILT) held on 20 October
2009. Here are no findings on the state of maintenance of the helipad
determined. A regular inspection of the platform on the day of the accident has not
planned. After the accident the ILT carried out an inspection on these points. The result of this
inspection was that the platform did not meet a number of statutory requirements and should be
disapproved for use as helicopter airport. The main rejection points were:
The platform was on the south side partly subsided.
At least 170 points were the (platform) boards loose on the metal supporting
construction.
Multiple boards were warped so that the planks above the surrounding planks
sticking (height).
Some parts of the metal supporting structure exhibited elastic behavior.
5
RESEARCH AND ANALYSIS
Technical research helicopter
The day after the accident, the helicopter salvaged and locally restricted investigated. Immediately after the
salvage his first flight control checked and it was found that the friction of
the collective was removed. This is determined unambiguously since it concerns a lever with two
positions. The position of the cyclic friction is not unambiguously determined. This is adjustable with
a knob, which no marks are applied. The friction can only be felt
determined. The helicopter has nearly 24 hours underwater. Its influence on the friction
of the cyclic has not been studied. The set resistance at the time of the accident is not
precisely determined. Thus, it is less clear later to determine whether the friction at the time
of the accident was completely loose and what influence the position of the friction has had on the
occurrence of the accident.
After the study site, the helicopter transported to a hangar where the next day
technical examination of the helicopter is performed. And no findings of issues
that indicate a technical cause of the accident.
Weight and balance
The maximum takeoff weight of the PH-WQW was 1,089 kilograms and the permissible load
up to 424 kilograms. With a total weight of the pilot, passengers and baggage of 228
kilogram (according to the load sheet) and 100 kg of fuel (estimate), the load current
approximately 328 kilograms, or 77% of the maximum permissible load. The focus was
within the prescribed limits.
The helipad
The planks of the platform were several places partly because bolts were loosened
broken. Since each shelf with several bolts were confirmed, resulting loose bolts
not directly in loose boards. There are no indications that the height of the
planks, the skids are hooked behind the shelves. On the platform were clear
slide visible traces of the skids. Having regard to the mass of the helicopter relative to the
mass of the platform, it is not likely that local resilient behavior of the platform
essential influence on the behavior of the helicopter. In summary, this means that,
although the platform (no longer) met the statutory requirements, it is unlikely that the
accident was caused by the condition of the platform.
The flight
At the start of the flight was the helicopter on the helipad with the longitudinal axis in a
direction of about 115 degrees (see Figure 6). The wind came from a direction between 330 and 360
degrees at a speed of 6 knots and gusts to 12 knots. This corresponded to an
relatieve4 wind region of 215 to 245 degrees (see Figure 7). With operations in this region there is wind
risk of unexpected movement to the top axis (weathervane effect). This is particularly true if the
helicopter already somewhat detached from the ground. The risk of unexpected increases in rotation
a situation with a low rotor speed, whereby the effectiveness of the tail rotor is limited. If the
pilot does not immediately respond, this can lead to loss of control of the helicopter.
Normally this will happen in a flight mode ("hover") or at a very low speed. In the
case with the PH-WQW had the helicopter ground contact which normally
prevents rotation about the normal axis.
4 is relatively with respect to the longitudinal axis of the helicopter.
6
Figures 6 and 7: PH-position WQW on helipad and risk vane effect (source: Google
Earth and FAA Handbook)
What is striking is that the main rotor in the startup phase had an unusual position (see Figures 8 and
9). Normally, during this phase the angle of the rotor with respect to the horizontal plane
limited. In the photos it can be seen that this angle is nearly equal to the maximum permissible angle
forward. This is only possible when the cyclic during the startup phase the kite in a wide
the neutral point lying is maintained.
Figures 8 and 9: the PH-WQW during startup, photos taken from the terrace
(Source: M. Westveer)
Such a position of the main rotor in the startup phase generates shaking the main rotor,
as the pilot. It is possible that the pilot in the cyclic with the search for the
"Neutral point" during startup, the collective is no longer kept up pushed down.
At 60-70% rotor speed generated by the main rotor collective drawn sufficient lift to
sliding movements and rotations about the relatively smooth, wooden platform as possible.
The helicopter manufacturer indicates that at a rotor speed of 80% of the available torque tail rotor
only 50% of the pull at 100% rotortoerental.5 This was the
tail rotor may not be effective enough to keep the wind against the vertical tailplane against
work. Possibly this effect is reinforced by the helicopter, the counter-clockwise rotation, in a
wind region ended with the airflow through the tail rotor may not be evenly
and stable. This effect was enhanced by the collective drawn.
5 Robinson Safety Notice, SN-34, Revision April 2009.
7
When the rotation about the top axis increased and the pilot lost control of the helicopter, it was
pulling the collective not effective enough to stop the rotation, even though the rotation of the
probably something has reduced. This is due to the effect that, in the counter-clockwise
of the respective helicopter rotor system, the hull will start to rotate clockwise in response to the
torque applied by the motor to the rotor is carried out. Once the helicopter approximately 270 degrees
to the normal axis was rotated, came the helicopter, low-power, fully independent of the platform
and made a left turn, after the helicopter hit the water. The pilot stated there
have chosen the helicopter with low power regardless of the platform to come to
to prevent this at the edge of the platform would be possible, and there would fall off.
CONCLUSION
There was no evidence for a technical cause of the accident. It is also not
likely that the maintenance of the platform caused the accident.
Probably kept the pilot during startup in a cyclic before the neutral point located
position, with vibrations of the helicopter as a result. When searching for the neutral point is the
collective may not be fully held pressed down, allowing only elevator was
generated. When the increase of the rotor speed (and the elevator) increased the friction between the relatively
smooth platform and the chassis. Then could vane effect a rotation about the normal axis
initiate, so the pilot was surprised and his workload was increased. Then came the
helicopter in a region where the wind flow through the tail rotor is not uniform and
stable, as the workload of the pilot further increased. On turning and sliding responded
The pilot then inadequate. With a low rotor speed, the helicopter apart from the
helipad after an uncontrolled flight phase with insufficient power followed,
with hitting the water as a result. A single cause for the occurrence of the accident could
not be determined.
It is concluded that the pilot in the startup phase control of the helicopter lost and
the control failed to recover. Or possibly partly present friction of the cyclic
influence on the actions of the pilot, could not be determined.
DOWN PAID DURING START
In the Netherlands, it ensures the risk of accidents and incidents as much as possible
limit. When it (almost) goes wrong, can be prevented by repetition, regardless of the
guilt, properly investigate the cause. It is then important for the investigation
independent of the parties takes place. The Safety Board chooses
therefore his own investigations and taking into account the dependency of citizens
compared to governments and businesses. The Council has in some cases required by law
research.
GENERAL INFORMATION
Occurrence: 2012029
Classification: Accident
Date and time1: March 25, 2012, around 14:30
Place of incident: Near Zwolle
Aircraft registration: PH-WQW
Aircraft Type: Robinson R44
Type of aircraft: Helicopter
Type of flight: Passenger Flight
Phase of flight: Start
Damage to aircraft: Significantly
Number of crew: A
Number of passengers: Two
Injuries: None
Other damage: None
Lighting conditions: Daylight
SUMMARY
The pilot of the helicopter with registration PH-WQW had the intention to make a flight with
passengers of Lelystad Airport (EHLE) to a helipad near Zwolle and back. During
starting the helicopter for the flight back to Lelystad, the helicopter began to shake
and to bounce and move the helipad. The driver tried the helicopter
to stand out from the platform, but a low rotor speed unit could not
maintain height. The helicopter came next to the helipad in a puddle right where
it just floated. The occupants were uninjured left the helicopter and to the side
swimming. The helicopter later sank to the bottom of the pond, and was the following day
salvaged. The unit became significantly damaged.
1 All times in this report are local unless otherwise stated.
2
FACTUAL INFORMATION
The flight and the accident
On the day of the accident, the pilot flew the PH-WQW along with two passengers
Lelystad Airport to a hotel with a restaurant, situated on a lake, near Zwolle. Directly
adjacent to the pond is a helipad. The flight from Lelystad to the
destination and landing on the helipad went without problems. The pilot flew
the platform in a northwesterly direction (against the wind), carried above the platform
rotation and put the helicopter then the platform, with the nose in eastern
direction, the direction of more than 100 meters terrace. The pilot and passengers spent
about an hour on the terrace by which they had a view on the helicopter. According to the pilot
He has all that time no one at the helicopter copper seen and no details were observed.
After the pilot had the passenger boarding the flight to Lelystad, he performed
a "walkaround" inspection. This was less extensive than the first flight because
though the pilot had flown the helicopter and then no one had seen the device. The
driver was right and the passengers were left to rear left. The pilot stated that he
when starting the checklist had followed the pedals were neutral and that cyclic2 and
collective3 friction were selected. Due to the sunny weather was the right door open to
prevent the temperature in the cockpit too high up. Then, with the
right door open, the engine started. The pilot stated that he intended the door
shortly before departure to close and open the door has not affected him further. The throttle
stood up after the start-up of the motor in the stationary state, after which the coupling of the motor
the rotor was turned. The rotor began to turn and the driver suggested by the
throttle the engine speed to about 60%.
When the link was successful was the pilot, according to his statement, continue the finishing
of the checklist including the reduction of the friction of the cyclic and of the collective. From
that time, the helicopter began to shake and to the left on the helipad.
According to the pilot felt the shaking same as when the rotor rotates and the cyclic
not 'neutral' state. The driver responded by using the cyclic to search for the "neutral point".
This had no effect, it was shaking violently and the helicopter began from one skid on the
other to bounce and further to the left with a slow twisting motion to the left.
The passenger sitting next to the driver was said that the rotor blades at that time less
spinning around than at the departure in Lelystad. The helicopter finally turned around 270
degrees counterclockwise and moved to the edge of the helipad.
To prevent the helicopter from the platform would fall, the driver pulled the collective
up for the purpose of the helicopter independently of the platform to come. The pilot stated that
it away from the edge and wanted to move back slightly. After the collective was up
drawn, the helicopter began to climb and a turn to the left to make. During this
began to maneuver the helicopter an up and down motion in order to make the transverse axis. Then
dropped the phone. The pilot stated that he had pulled up on the collective
when the helicopter hit the water. The pilot can not remember the hit, but
his feeling was not hard. The unit was initially on the right in the
water float. All occupants climbed through the left side of the helicopter and swam to the
side where they were picked up by bystanders. The pilot left the helicopter last.
Everyone remained unharmed. The helicopter then sank to the bottom of the pond, and was
a day later salvaged. The unit became significantly damaged.
2 The cyclic is the control organ with which the movement in the horizontal plane is controlled. The cyclic is
equipped with an adjustable friction (resistance) to prevent accidental movement.
3, the collective is the control organ with which the movement in the vertical plane is controlled. The collective is
equipped with an adjustable friction (resistance) to prevent accidental movement.
3
Figures 1 and 2: the PH-WQW shortly before it hits the water (source: M. Westveer)
The aircraft
The Robinson R44 is a four-seater helicopter powered by a piston. The chassis
consists of two metal beams, called skids.
The driver
The driver was in possession of a valid license for private pilot on
helicopters. He was also in possession of a type rating for the Robinson R44.
Number of hours in total 173
Number of hours by type 173
Number of hours during last three months 4
Table 1: Experience driver PH-WQW
Weather
According to data from the Royal Dutch Meteorological Institute (KNMI), the wind
near Zwolle during the accident from a northwesterly to northerly direction (330-360 degrees)
with a speed of 6 knots with gusts of 10 to 12 knots. The temperature was 13
degrees Celsius and visibility over 10 km.
The helipad
The helipad consisted of a metal structure which hardwood planks were
screwed. The platform has been for more than 50% surrounded by the water of the pond.
Figure 3: the helipad (source: Google Earth)
4
After the accident were warped boards found whose confirmation was partly
disconnected. Also had the support of the steel structure at some points subsided. On the
platform slide tracks were found.
Figure 4: partially loose board Figure 5: slide rails
For the helipad was called Airport Regulations issued by the county
Overijssel which meant that the platform could be used for performing takeoffs and
landings with helicopters. The Inspectorate for Environment and Transport (ILT) is responsible for monitoring
on the establishment, equipment and the safe use of the helicopter airport. The last inspection
was by IVW (the predecessor of the ILT) held on 20 October
2009. Here are no findings on the state of maintenance of the helipad
determined. A regular inspection of the platform on the day of the accident has not
planned. After the accident the ILT carried out an inspection on these points. The result of this
inspection was that the platform did not meet a number of statutory requirements and should be
disapproved for use as helicopter airport. The main rejection points were:
The platform was on the south side partly subsided.
At least 170 points were the (platform) boards loose on the metal supporting
construction.
Multiple boards were warped so that the planks above the surrounding planks
sticking (height).
Some parts of the metal supporting structure exhibited elastic behavior.
5
RESEARCH AND ANALYSIS
Technical research helicopter
The day after the accident, the helicopter salvaged and locally restricted investigated. Immediately after the
salvage his first flight control checked and it was found that the friction of
the collective was removed. This is determined unambiguously since it concerns a lever with two
positions. The position of the cyclic friction is not unambiguously determined. This is adjustable with
a knob, which no marks are applied. The friction can only be felt
determined. The helicopter has nearly 24 hours underwater. Its influence on the friction
of the cyclic has not been studied. The set resistance at the time of the accident is not
precisely determined. Thus, it is less clear later to determine whether the friction at the time
of the accident was completely loose and what influence the position of the friction has had on the
occurrence of the accident.
After the study site, the helicopter transported to a hangar where the next day
technical examination of the helicopter is performed. And no findings of issues
that indicate a technical cause of the accident.
Weight and balance
The maximum takeoff weight of the PH-WQW was 1,089 kilograms and the permissible load
up to 424 kilograms. With a total weight of the pilot, passengers and baggage of 228
kilogram (according to the load sheet) and 100 kg of fuel (estimate), the load current
approximately 328 kilograms, or 77% of the maximum permissible load. The focus was
within the prescribed limits.
The helipad
The planks of the platform were several places partly because bolts were loosened
broken. Since each shelf with several bolts were confirmed, resulting loose bolts
not directly in loose boards. There are no indications that the height of the
planks, the skids are hooked behind the shelves. On the platform were clear
slide visible traces of the skids. Having regard to the mass of the helicopter relative to the
mass of the platform, it is not likely that local resilient behavior of the platform
essential influence on the behavior of the helicopter. In summary, this means that,
although the platform (no longer) met the statutory requirements, it is unlikely that the
accident was caused by the condition of the platform.
The flight
At the start of the flight was the helicopter on the helipad with the longitudinal axis in a
direction of about 115 degrees (see Figure 6). The wind came from a direction between 330 and 360
degrees at a speed of 6 knots and gusts to 12 knots. This corresponded to an
relatieve4 wind region of 215 to 245 degrees (see Figure 7). With operations in this region there is wind
risk of unexpected movement to the top axis (weathervane effect). This is particularly true if the
helicopter already somewhat detached from the ground. The risk of unexpected increases in rotation
a situation with a low rotor speed, whereby the effectiveness of the tail rotor is limited. If the
pilot does not immediately respond, this can lead to loss of control of the helicopter.
Normally this will happen in a flight mode ("hover") or at a very low speed. In the
case with the PH-WQW had the helicopter ground contact which normally
prevents rotation about the normal axis.
4 is relatively with respect to the longitudinal axis of the helicopter.
6
Figures 6 and 7: PH-position WQW on helipad and risk vane effect (source: Google
Earth and FAA Handbook)
What is striking is that the main rotor in the startup phase had an unusual position (see Figures 8 and
9). Normally, during this phase the angle of the rotor with respect to the horizontal plane
limited. In the photos it can be seen that this angle is nearly equal to the maximum permissible angle
forward. This is only possible when the cyclic during the startup phase the kite in a wide
the neutral point lying is maintained.
Figures 8 and 9: the PH-WQW during startup, photos taken from the terrace
(Source: M. Westveer)
Such a position of the main rotor in the startup phase generates shaking the main rotor,
as the pilot. It is possible that the pilot in the cyclic with the search for the
"Neutral point" during startup, the collective is no longer kept up pushed down.
At 60-70% rotor speed generated by the main rotor collective drawn sufficient lift to
sliding movements and rotations about the relatively smooth, wooden platform as possible.
The helicopter manufacturer indicates that at a rotor speed of 80% of the available torque tail rotor
only 50% of the pull at 100% rotortoerental.5 This was the
tail rotor may not be effective enough to keep the wind against the vertical tailplane against
work. Possibly this effect is reinforced by the helicopter, the counter-clockwise rotation, in a
wind region ended with the airflow through the tail rotor may not be evenly
and stable. This effect was enhanced by the collective drawn.
5 Robinson Safety Notice, SN-34, Revision April 2009.
7
When the rotation about the top axis increased and the pilot lost control of the helicopter, it was
pulling the collective not effective enough to stop the rotation, even though the rotation of the
probably something has reduced. This is due to the effect that, in the counter-clockwise
of the respective helicopter rotor system, the hull will start to rotate clockwise in response to the
torque applied by the motor to the rotor is carried out. Once the helicopter approximately 270 degrees
to the normal axis was rotated, came the helicopter, low-power, fully independent of the platform
and made a left turn, after the helicopter hit the water. The pilot stated there
have chosen the helicopter with low power regardless of the platform to come to
to prevent this at the edge of the platform would be possible, and there would fall off.
CONCLUSION
There was no evidence for a technical cause of the accident. It is also not
likely that the maintenance of the platform caused the accident.
Probably kept the pilot during startup in a cyclic before the neutral point located
position, with vibrations of the helicopter as a result. When searching for the neutral point is the
collective may not be fully held pressed down, allowing only elevator was
generated. When the increase of the rotor speed (and the elevator) increased the friction between the relatively
smooth platform and the chassis. Then could vane effect a rotation about the normal axis
initiate, so the pilot was surprised and his workload was increased. Then came the
helicopter in a region where the wind flow through the tail rotor is not uniform and
stable, as the workload of the pilot further increased. On turning and sliding responded
The pilot then inadequate. With a low rotor speed, the helicopter apart from the
helipad after an uncontrolled flight phase with insufficient power followed,
with hitting the water as a result. A single cause for the occurrence of the accident could
not be determined.
It is concluded that the pilot in the startup phase control of the helicopter lost and
the control failed to recover. Or possibly partly present friction of the cyclic
influence on the actions of the pilot, could not be determined.
Last edited by Dynamic Roller; 28th Mar 2013 at 16:36.
