Canadian Safari kit-built ATSB report accident 23Mar03

[Victor Duarte]

Found on a helicopter site

Canadian Safari kit-built ATSB report accident 23Mar03

quote:
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FACTUAL INFORMATION

Sequence of events

The pilot and a passenger of a kit-built Canadian Home Rotors Safari (Safari) helicopter, registered VH-VDB, operated as an experimental aircraft1, were making a private flight from the pilot’s property to a nearby airstrip.

At about 1415 Central Summer Time, witnesses reported seeing the helicopter flying in a south-westerly direction, at an estimated height of between 100 and 200 ft above ground level. The helicopter was in steady, level flight and sounded normal. Witnesses reported that the flight path was one regularly flown by the pilot. Weather conditions at the time were clear, with a light breeze and a temperature of approximately 24 degrees C.

One witness, who knew the pilot, reported that he saw the helicopter commence a gentle left turn and the pilot waving2 to him moments before it broke up in flight. That witness also reported seeing the cockpit bubble shatter and a cloud of white dust appearing from the area of the cabin. Witnesses reported having heard the engine operating immediately prior to and following the in-flight break-up. Other witnesses heard a loud metallic sound, and described the helicopter almost stopping, pitching nose-up and a main rotor blade folding(?), before pitching nose-down and descending steeply. The helicopter collided with a large tree and a shed before impacting the ground at the rear of a residential house block. There was no fire. Both occupants were fatally injured.
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and


quote:
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ANALYSIS

Damage to the main rotor system was consistent with both main rotor blades having failed in upward bending overload, in excess of design limits, and the main rotor diverging from its normal plane of rotation and contacting the tail boom and canopy.

Examination of the helicopter and its transmission and rotor systems found no evidence to indicate any pre-existing defect that could have contributed to the in-flight break-up. Witnesses reported hearing the engine running before and after the break-up occurred.

The pilot was seen waving just moments before the helicopter broke up. The investigation was unable to determine if flight control input by the pilot or passenger, or lack of corrective control, had contributed to the development of the accident. Although either low rotor RPM or abrupt manoeuvring can result in air loads on the blades exceeding their design limit, the reason for the excessive upward bending of the blades could not be determined.

The NTSB special investigation report NTSB/SIR-96/03 - Robinson Helicopter Company - loss of main rotor control accidents, which analysed accident data from 31 fatal accidents, concluded that in the absence of any evidence of defects or component failures, other possible factors such as the sensitivity and responsiveness of the helicopter’s flight controls combined with limited pilot skills, proficiency, or alertness, be considered. Although that report concerned a different helicopter type from the Safari, its conclusions were directed to all lightweight helicopters with sensitive and responsive controls, characteristics shared by both types.

The installation of a governor and an aural low rotor RPM warning, as noted in the NTSB special investigation report NTSB/SIR-96/03 - Robinson Helicopter Company - loss of main rotor control accidents, had contributed to the greatly reduced incidence of low rotor RPM related accidents in that helicopter type.
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link :http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=568

[quadrirotor]

A simple car cruise control used as a rrpm can solve this problem. There are some cruise control which are full electric, they are found in the Hot Rodding car domain...
http://www.julianos.com/cruise_control.html

[Vance]

Victor, in this Kit, the piolt normaly controls the throttle and the collective and is suposed to keep the rotor within limits. The Robinsons I have flown all did it automaticaly. In either one you have to be carefull about low rotor rpm. A rotor stall is a non recoverable event. Even in the Robisnon you have to manage your rotor rpm. This is one of the down sides of collective pitch adjustment. In a Robisnon or a Safari, I have flown both, I would not take my hand off of either the colective or the cyclic in flight because things can detiorate very quickly. In an Autogiro I still like to hold the cyclic and the throttle, but only because I have a low fear threshold.

Andre's fix, in my opinion, would not respond fast enough to be truely usefull. Even in a Robinson it is not hard to get ahead of the govenor. Thank you, Vance

[Victor Duarte]

Vance, understood, in the original b47, the gases were not "compensated" a far as i remember, in turbines they are automaticly regulated.
there are rpm stabilizators , how does the r22 work? mechanic link or other ?

do you think the blade folding is due only to the rpm loss or isn't it a little weakness? talking about possible low design limits..

thanks

[Vance]

Victor, I don't know how it works, but I can tell you it works well, you can feel the twist grip respond when you pull colective. It is made so you can overide it with the twist grip and if you pull collective too fast, it can't keep up.

I thought that manually managing the throttle would be a challange, but in a Hiller or a Bell 47, with their heavy wood rotor it is an easy skill to learn. Things change fairly slowly. In a Helicopter with a light rotor, rotor rpm is a little more transiant. It is still not a hard skill to learn. Vigilance is the hard skill to maintain. Thank You, Vance

[Victor Duarte]

Vigilance is the hard skill to maintain.
damn humans... always the main source of failure... sadly

in my books relating these problems of gas compensation, they describe a simple centrifugal device : two weights kept up by rpm dont input onthe throttle, but if the rpm decreases, the weights input on the throttle by a kind of push/pull ... ever seen that kind of device?
thanks

[Vance]

I built a steam engine when I was seven and it used this type of governor with weights that would swing out, push on a rod and reduce the volume of steam that reached the piston. When it was running at peak rpm the weights would be straight out. I believe that is where the term "balls out" comes from. Thank you, Vance

P.S. The boiler blew up when I allowed the presure to get too high in an effort to get more torque. It took out most of a wall and part of the roof. The boiler was made of brass and soldered. This is not best practice.

[Jerseywing]

The same style using weights are still used to control elevator speed (old ones in NYC-I didn't believe it when I saw it but it's true) and overspeed controls on steam turbines. I have some boiler experience but I'm used to making steam with zoomies. Same principle is used in centrifugal clutches on B&S engines for mini-bikes

[quadrirotor]

The Mosquito and the AW95 use them with engine whose torque curve is not favorable at all!...so if you wonder anything...I was told that Safari does so now...
http://www.innovatortech.ca/mosquito_gallery.html

[Victor Duarte]

what is this box ?

I think all injection calculators can automatically maintain RPM, if correctly programmed. carbs are other mess..

[Vance]

Victor, most gas injectors also use a mechenical throttle, which still needs to be actuated to change power output.

Andre, One of the Safaris that I flew was the company demo at last years Sun n Fun and it did not have a governor. Throttle management was not dificult. It flew very well and was easy to fly. I think that it is a very nice helicopter. It is not hard to over reach any of the governors I have tried. It is no substitute for pilot vigilance. Failure to maintain rotor rpm over a faily narrow range has very serious consequences. Too fast and you damage a very expensive rotor system, too slow and down you go. Even in autorotation the rotor speed must be managed. I like to have that off my plate and that is another reason why I like autogiros best.
Thank You, Vance

[Victor Duarte]

I trust you, vance, sounds a good helico anyway. like the original. to put between every hand ? of better be skilled enough?

I was also pointing the folded blade in the acc. report. In an other thread, here, (sportcopter blades on a mini 500) , they also told about blade grip problems, i was wondering if the babybelle could had a similar default.

do you think the pilot may have tried a brutal flare and/or entered a ring vortex stall, so, it could explain he tried to override throttle/collective.

thanks

[Vance]

Victor, I believe that when the blades stall the drag goes dramaticaly, the blades slow very quickly and lose their strength that comes from centrifugal force. They flap as they are slowing down and begin to hit things and then bend upward as the machine decends.

I had not herd of any blade grip problems. I beleive that you are speeking of using autogiro blades on a helicopter. The blades them selves need to be stronger at the root because of all the extra forces on a driven rotor.

I am not comfortable with speculating on someone elses accident since I wasn't there . I will try to imagine the events as described with me as the pilot. I wave at someone on the ground and have let go of the colective. I am not paying attention to my flight instruments. I have not done a sweep in a while. My rotor speed is decaying from my last colective adjustment and I don't notice. By the time I do notice it is too late and I don't even have my hand on the colective (throttle). It is now too late to drop the colective and way to late to increase throttle. The blades start hitting things and I know that my friend and I am about to die.

I like autogiros best! Thank you, Vance

[Victor Duarte]

Vance, gyros are more and more attractive to me ;)

If i asked these questions, it is because i just wonder and search what is the static limit of resistance for a blade/grip.. I know all rotors are designed , dealing ideally with the expeted forces.. but unfortunately all the accidents come from messing with these frontiers, and passing them.

My thinking is : why so tight limits (weight, ok ) and why not to secure a little more these kind of unexpected events...

I know even an unbreakable blade wont prevent stall and fall , just another of my paranoid questions...

thanks for your explanation.

[Vance]

Victor, Spend a little more time on the NTSB site. The biggest cause of helicopter crashes is wire strikes. Second common one is blade strikes against something on the ground. Rotoway has a problem with the main drive, the tail rotor drive and the cooling system. Rotoway also seems to have a lot of engine outs with unsuccesfull auto rotation. This is sometimes a pilot skill issue and some times it is the terrain they are flying over, which still involves poor aviation decision making. If you are flying over somewhere where you can't land fly high enough to glide to somewhere you can land. Running out of fuel is also common. In my first half hour of ground school I learned how to prevent most of the accidents that don't involve mechinacal failure. My favorite excuse for destroying a very expensive helicopter is a fellow who was flying up a river and hit wires. He said that "I saw the poles but I never saw the wires untill I hit them." I am not sure what other use he thought the poles had.

Back to your real question. Helicopters for civilian use need to be light so they don't cost quite so much to operate. A Robinson r22 Beta weighs 855 pounds with a four hundred pound engine. 455 pounds for the frame, body tanks main rotor, tail rotor drive system, controls ect. with 178 pounds of fuel on board (29.7 galleons) it will lift 337 pounds of baggage and people. I weigh 230 so I can't fly with my wife unless she weighs 107 pounds. My instructor was fatter, but thankfully shorter and we never got to fly with a full tank of fuel in the R22. It has 131 horsepower. Anything that you do to make the helicopter stronger makes it weigh more and carry less. Inertiail loads go up by the square of the increase in speed, so to make the rotor stand an overspeed better adds more weight which means it needs to be even stronger/heavier which of corse means it carrys less. You can put a bigger engine in it but that makes the gear box heavier and the anti torque rotor has to have more athority(heavier). You have to carry more fuel. By now it needs a bigger rotor and that takes a stronger(heavier) rotor head with bigger heavier rotor blades. It may be time for hydralicaly boosted controls(heavier).

Helicopters come with a very big (heavy) rule book that should be caried in the aircraft and obeyed at the risk of great finantial cost or even death. As long as you follow the rules your chances are pretty good you will not have an incident. My Robinson dealer publishes a monthly news letter that includes the NTSB reports of all certified helicopter incidents that have been reported. He wants his customers to learn from other peoples mistakes. I personaly know of several helicopter incidents where they cleaned up the mess realy fast so they didn't get caught not reporting to the NTSB. Helicopters are already well designed. There is just a big price to pay for being able to hoover for a few minuets per flight.

This brings us to the height velocity curve. One of the rules In an R22 is don't hoover above 5 feet and below 500 feet. Foward motion is what makes the flying safer between 5feet and five hundred feet. If you see a light helicopter taking off straight up or landing straight down they are braking one of the rules and if the engine stops they have at the very least spent a lot of money.

I like Autogiros best. Thank you, Vance

[scott heger]

I have two good helio accidents that happened within the last few years that were told to me at the Bell Helicopter Acadamy. #1 a guy was towing a water skier across a lake with a Jet Ranger using the cargo hook. The skier let go, and the rope "bungied" up into the tailrotor blade. It chopeed off one blade, which caused a inbalance, and severed the entire rear boom. ....KER-splash!!!! The second one was on Kauai. The commercial pilot had dropped off his tour group at the Passenger Terminal of Lihue(KLIH) Airport. The helicopter company maintained a parking area on the opposite side of the field. The Bell Jet Long Ranger was dirty, so on the way the pilot decided to wash it off inflight using the high pressure sprinklers(rain-bird style) of a neighboring sugar cane field. He went threw the first time, and did not quite get it clean enough, so he turned around and went a second time. However he put the water stream right at the air intake to the engine by mistake. The engine flamed out , and at 50 feet and low airspeed, the rest was history...pow. A 1.1 million dollar helicopter destroyed because he didn't feel like washing it the right way. Common sense went out the window on both of these.

Scott Heger, Laguna Niguel, Ca N86SH

[Victor Duarte]

Vigilance is the hard skill to maintain.
I would add : stupidity is a skill hard to delete.
Scott, a pity ..long ranger..tss , are they so "overbored" with helicos that they forget the price of the toy...
Vance thanks for the long post, just like if i was the passenger.
cheers

[Ted Eggleston]

Found on a helicopter site

Canadian Safari kit-built ATSB report accident 23Mar03

link :http://www.atsb.gov.au/aviation/occurs/occurs_detail.cfm?ID=568

At the time of this accident, I was involved in building a Safari with Paul Scells. Paul had recently spent some time ( a month earlier) with the pilot, who at that time was the Australian importer and distributor for Safari's.

Initial reports couldn't confirm whether the father or son had operating controls, but it was enough for us to put our bird away for a period of five months as we tried to understand what actually happened. We eventually finished the Safari but were very concerned about its capabilities until the mandatory 40 hours hovering flight time has passed.

Tracking blades was a ritual of holding a pvc pipe up with a zip tie attached, with a dob of grease added, with slow upward movement until contact was made. Then we would adjust the offending blade, clean off the grease mark and start again. Kneeling under the blades wasn't a pleasant thought after thinking about the South Australian accident. But since we didn't know how else to track the blades....

Ted

[Victor Duarte]

Thanks for the imput, Ted, being so close of the heatpoint, you have prime info.

You said it was the aussie dealer ? do you think it could have been a "macho" demonstration turned to failure ?

About blade tracking, i helped in some, we used a paperboard on a wood stick, on the ground, and two coloured charcoals blue and yellow for each blade tip (bell47), then rotor on, the paperboard was gently pivoted in order to touch the blades, then we could know whitch blade was up or down and adjust flaps.

I also heard about the use of a strobe lamp, with color fluo markers..

thanks ted

[Ted Eggleston]

Victor,

We have always suspected that the son was flying as PIC but we'll never know. The father was the importer and distributor and he was reponcible for building the kit in which they died. By all reports, the machine was beautifully built, however there was a question about rotor blades arriving into Australia that had a breather hole in the tip end. I personally, never saw the Safari that this guy built (apart from a photo), but if it did indeed have holes as had been described to me, and had been subjected to weather then perhaps this may be partly responcible.

I must add here that this is pure conjecture on my part and has arisen only in passing conversation with Paul, who had a flight in the destroyed aircraft about 6 weeks prior to the accident.

Ted

[birdy]

"I like to have that off my plate and that is another reason why I like autogiros best."
We think alike Vance. ;) :D

[Aussie_Paul]

Me to Birdy. Besides I couldn't afford a chopper. I am only a simple gyro instructor turning my wifes large wage into a small one with me toys!!!!

Aussie Paul. :)

[Vance]

Thank you Birdy, I will take that as a compliment. I admire you as a pilot and a person.

Victor, The way I deal with my fears is to figure out why the same thing wouldn't happen to me. I feel like you are looking for a big reason why this happend. If it was rotor speed it is a small thing. It is just a matter of not paying enough attention to the rotor tach.

In the crash I imagined there were several contributing factors, but all small mistakes. I havent learned to be sensitive enough to where I could tell my rotor speed without looking at the rotor tach. Looking in my Robinson R 44 manuel, maximum, powerd rotor speed is 102% (404 rpm) minimum powerd rotor speed is 99% (392 rpm) In autorotation maximum rotor speed is 108% (428 rpm) mimimum rotor speed in autorotation is (356 rpm). In poward flight this is a only 3% mistake and you can't recover. At 200 feet they were too low to enter autorotation. They are at the wrong end of the height velocity curve. When I was imagining I was the pilot if I started to sink my instinct would be to pull collective and add throttle because that is how you climb. This would be exactly wrong if my rotor rpm had had decayed because the colective is imediate and the engine takes a while to power up. As I continued my natural tendency would be to pull more collective as I continued to decend. My training would have a fight with my instinct. It needs to be a very short fight. I needed to add throttle and drop collective. That is why the powerd rotor limits are so much narrower. I needed to address the low rotor rpm before anything else. I should have had more altitude so that I had more options. If I was going fast I could have done a quick stop to trade away foward speed for rotor energy (rpm). Doing an autorotation from 200 feet limits your landing options. I don't have a lot of time to make any of these decisions. Small mistakes, but for me,the potential for problems and the consiquences of wrong decisions takes some of the fun away and I want my gyro back. It is aparant that they had made a choice, that I consider to be a poor aviation decision, of flying at 200 feet agl many times before. It lowers the helicopters tolerance for other polot errors.

Please don't misunderstand me, I love to fly Helicopters, I love flying autogiros even more. The challange of doing a complex task corectly has an allure, but I feel it is important to understand the consequences of small mistakes.

I know we have a lot of helicopter enthusists here, so please jump in here if I am misanderstanding or overstating something. Thank You, Vance

[Victor Duarte]

Paul, you promised me a picture of your landing gear and you send me your pic! :mad: :D :D

Vance, you're right about what i wanted to hear , or not, about this incident, not looking for "sensationnal" but, as you guessed, ask if ther is not something criticizable in the head design.. my opinion is not made yet.
the other question is : you talk about a possible sinking, due to what ? possible "rodeo" piloting ? i don't accuse, as you say, we learn from mistakes.

Interestiing, the way you "pre-live" your flights, i also tried to figure my reactions virtually. Aerobatic pilots do this before each flight.

i keep 3 points :

- the tiny range between the two safe borders 3 % (in r44) sounds tiny for public use... usual ?

- the fear : like in PIO, it can be source of bad inputs, over-control.
but, try to keep your hands on a snake's cage while it attacks... human inner reflex, hard to overcome without trained reactions..

- the fact that the evaluation you make of the events rollback make me think , the person was perhaps more used to bigger turbine helicos with more power reserve and auto rpm stab. I think this person didn't learn on a B47.

I also love helicos, nothing wrong to dig the facts.
other opinions wallcome.
thanks

[Vance]

Victor, I used the sinking as the reason I made the wrong decision and hastened the decay in rotor rpm that preceded the blades striking the helocopter body. When I am flying low in a Helicopter I try to be more precise in the control of my altitude. Any increase in colective will slow the rotor. To be more clear, if you notice that your helicopter is sinking and the reason is rotor rpm decay, it is probably too late.

I don't think very fast and getting behind an aircraft is not best practice. If I have practiced a procedure I can live to think slowly another day. When I was racing my streamliner at Bonneville I had to plan the entire run, including parachute deployment and cross winds at the gap, before I ever rolled off the line. This leaves more of my mental capicity to reconize and deal with anomalies. At 300 miles per hour I am traveling at about 440 feet per second. I am so low that the track goes over the horizan about 75 feet out. This doesn't leave a great deal of time to ponder. There is no substitute for practice and planing.

Acording to my Robinson 44 pilots operating manuel height velocity curve, I should not fly slower than 50 kts at 200 feet agl. at sea level density altitude I should not hoover between 8 feet and 400 feet agl, At 7000 feet density altitude I should not hoover below 600 feet agl.

Compared to an Autogiro, a helicopter is very unforgiving of inprecise piloting. Thank you, Vance

[brett s]

Getting slightly below 99% rpm in the R22 or R44 isn't going to kill you without warning - minimum demonstrated rpm in both is something like 80-85%. Remember that running at low rpm causes other problems than getting closer to blade stall - less hp available (in a piston ship anyways), less tail rotor authority, more stress on rotor components...

While I hate to guess at accident causes, this one sure sounds like low rpm - I've never seen blades fold vertically otherwise. The question will be why - pure pilot error or mechanical failure followed by pilot inaction. If you have a centrifugal clutch or other drive failure failure it can be tricky to diagnose at first - engine rpm will be climbing like mad while the rotor rpm plummets. I've seen a couple incidents like that first hand - a Bell 47 that lost the clutch & a Hiller 12E that broke the torsional coupling between the engine & transmission - the Hiller was just taking off & maybe 5' agl, so just a hovering auto (but the engine overspeeded to 4000+ rpm in an instant), the Bell 47 was an ag ship & in the middle of a turn at probably 100' and minimal airspeed. Pilot walked away, machine was totaled.

[Victor Duarte]

Brett , vance and others, did you see any case of blade folding in other accidents ?
thanks.

[Vance]

Bret, thank you for the corection. I re-read my post and realized I was saying that you crash if you fall below these limits. Robinson would like you to operate inside of their limits so you are not to close to disaster and are not tearing up equipment. I think it is important for the non helicopter flyers to understand how fast rotor rpm does decay and that with too much Colective the rotor can stall even inside of the proper rpm range.

Victor, vertical folding of the blades is not unusual in low rotor rpm crashes. Thank You, Vance

[brett s]

I've seen a few NTSB reports where the blades folded vertically - every single case was a pilot failing to lower the collective when the engine failed. You've got very little time in a low inertia rotor helicopter like the R22 before it gets too low to be recoverable, somewhere in the neighborhood of 2 seconds if you do absolutely nothing. Most of my flight time is in Bell 47's & Hiller 12E's but I did get my PPL in the R22...

All my time in the R22 was prior to the throttle governors being available - I can't imagine them being needed in them, the mechanical throttle correlation is better than any piston ship I've flown - the Bell 47 is pretty bad, there are a lot of places where slop can build up in the linkage & make it even worse. But like anything else it's just a matter of training, no big deal after you get used to it. Doing ag work I used sound for maintaining rpm a lot more than the tach, at those heights you don't look inside a bunch...