Chop tail off in the hover??
 

Left and right yaw followed by nose up and down and then tail chopped. That’s a dramatic sequence from what I understand to be an OGE, albeit low level, hover. Serious over controlling or could turbulence from the tree tops be wholly responsible?


https://atlantic.ctvnews.ca/pilot-de...rash-1.5343237

The report is here
https://www.tsb.gc.ca/eng/rapports-r.../a20a0027.html

They've highlighted LTE, presumably as they cleared the trees tail rotor entered the vortex from the main rotor blades

I don't get it?

Your friend decides to not land there because of the winds, so you decide to land there?

Nah, TTRW < 150. On type < 100. Nil HRS past 90 days.

I wouldn’t say he ”forgot” how to fly because at that hours he hadn’t ‘learned’ yet to fly.

Plus all the other signs of attitudinal incompetence: no medical (3 yrs expired) no flight log entries, ...

More money than sense. He was not so much PIC, more like DHIC.

Rules, regulations and common sense obviously didn’t apply to this pilot.

His medical was two and a half years out of date so he was unlicensed and presumably therefore uninsured. I feel sorry for his unknowing passengers.

The report states he was only 130 lbs under gross max weight at the time of the accident and this was when he was going for a refuel - what was his take-off weight when they started the trip then? Full fuel (110 litres)is just over 200lbs.

130lbs is only 5% below max gross and, adding in the relatively high temperature, he will have been working the aircraft quite hard to get into an OGE hover, let alone then climb vertically.

I wouldn't be surprised if he drooped the Nr trying to lift out of the confined area, slowing down the TR by default and reducing its effectiveness. Then, panic at the prospect of a non-existent TR malfunction led to some serious overcontrolling.

A very inexperienced pilot trying to do things way beyond his capabilities - again!

Shame the TSB muddies the waters by banging on about LTE - this clearly wasn't.

It was not hot at 23.6C (74.5F). It was not high, CCW5 is 350 ft MSL. Weight is 2370. That is well within the OGE hover performance limits of the R44.
https://cimg3.ibsrv.net/gimg/pprune....20584adec7.jpg

Full fuel is 47.7 USG or 180 liters assuming bladder tanks (it would be a hair more with the old tanks). Assuming there was room in the tanks for all of the 130lbs available that would be 21.6 gallons, or almost half tanks. However those numbers are probably meaningless because the report does not discuss the fuel state of the aircraft. But theoretically if he added 20 gallons that would give him well over an hour of additional flight time. Conservative planning for an R44 RII at max. gross, near sea level, 90KN, is about 15 gal/hr. That might have been exactly what he was seeking.

The weather conditions including winds were well within the limits of the machine. The max. performance take-off at max. gross would have required maximum pilot effort, though, if the trees are as high as reported.

It is unfortunately that this pilot did not choose to come in over the water above ETL with the wind on his right. Or make an approach to the water into the wind and hover taxi with a right crosswind up onto the paved ramp. Perhaps the paved ramp was full, or that he was untrained/unfamiliar with crosswind landings, or the fuel drums were in the confined area. Either way, a little unanticipated yaw, which is certainly possible, should not have lead to such wild pilot-induced oscillations that the tail was cut off, but no doubt I state the obvious.

What robbies are missing in the poh, is a chart that shows the average OGE pilot performance :}

That should be part of the training. The instructor should demonstrate that for the same manœuvre the students needs more power than the instructor. And explain why.

Just because the manual says the aircraft can doesnt mean your aircraft can. Please remember that the manual is derived from test pilots using a new helicopter with perfectly clean blades and a brand new engine, there ability is obviously beyond the majority of pilots with the manufacturer trying to make his machine's performance look really good

Certification takes the responses of the average bloke, or gal, into consideration.
There is always a margin for error.

aa777888 - when you say 'well within' you should qualify that with 'inside the limits of the performance graphs' since you can't tell how much spare performance there might or might not be from the graph, only that you reach the max gross weight line before you hit temperature or DA limits.

Just having OGE performance isn't enough for proper confined area operations like this with tall trees - you need to have a thrust margin of at least 5% and ideally 10% to allow for the manoeuvring and any turbulence/wind shear/recirculation.

My point about the fuel - and I took the 110litre fuel capacity from the Robinson site without realising there was an aux tank giving 180 - was that to get to where they planned to refuel, they would have used quite a lot and in all likelihood got airborne from Reeds Pond in excess of gross weight. It adds to the expired medical in terms of attitude to aviation.

How about this: the aircraft was capable of an OGE hover per the POH at approx. 4800 ft pressure altitude under the stated conditions, but it was landing at an altitude of 350 MSL. In my book that is "well within", others may have a different opinion.

Even stipulating that, it would not have been an issue in this case, both on paper and as someone who regularly flies an R44 at max. gross.

Looking at the distances involved, which even in a straight line without screwing around with the reported stops due to fog, is on the order of 340+ NM. That is beyond the no-reserve range of the helicopter which is 300NM (per the book). They would have had to stop for fuel during one or more of the stops they made as they scudded their way down the Labrador coast. If that was the case, then he probably wasn't over gross. But the report doesn't provide that level of detail. So we can't be sure. Nevertheless, over gross was not a factor in this accident.

Regardless, one cannot but agree that there was a significant lack of airmanship demonstrated.

Lazy feet and probably looking at the trees, then possibly gripping the throttle too tightly. With that kind of wind, weight and altitude, the 44 shouldn’t end up the way it did.

Bell ringer i think you find it doesnt and it certainly doesnt take into account an aircraft which is not new !

The performance charts I'm familiar with are always based on a zero engine. If you have a positive margin engine the chart will also accommodate this. If you have less than a zero engine you're off the chart, you can't fly, and maintenance is required. But that's for turbine engines. I don't know if engine trend monitoring is done on piston engines, or whether performance charts take into account the performance margin of the piston engine.

But you don't know how far within and what level of power margin it gives you - that is my point. Just having OGE performance isn't enough for confined area work. And his DA was about 1200'.

If you were doing a long transit like that in uncertain weather conditions, wouldn't you fill it to full (if you could keep within max gross). The report doesn't mention previous refuel stops but they had to go beyond where they originally planned to refuel so the chances of it being quite empty are higher and may explain why he chose to try and get in where he did.

It would be interesting to know if he did any pre-flight performance planning.

Poor airmanship, poor decision making and ultimately poor handling are the causes here - an inexperienced pilot biting off more than he can chew.

Military turbines have a Power Performance Indicator graph (PPI) and on the Sea King, the performance graphs were based on 94% PPI so as long as your engines were better than that, you were on the safe side of the line - very important for prolonged high hover work when winching.

Practically all my hours are in Robinson products. I can assure you that he had boatloads of margin. Plus, I find it hard to believe that if you looked at any OGE performance chart for any helicopter and saw a 5000ft DA differential between where it was operating and where it could operate OGE, as there was in this case, that you would not automatically believe that not only was there sufficient margin, but that there was a lot of it. Seriously, is there any helicopter that you know of or have flown that would not have provided sufficient margin under those conditions? And no corner cases like it was a hurricane or something. Just a plain old nice flying day like they had.

Didn't argue that, and still not arguing that. But it does stand to reason they had to refuel somewhere in Labrador for the trip to be possible. It would have been nice to see that information in the report, and also to know how the other helicopter managed fuel and payload, too, especially since the other helicopter never did refuel at the accident site.

Again, not arguing, totally agree. But I am much more focused on the inadvertent yaw induced panic that ultimately did him and his passengers in. That might have happened nearly anywhere in this trip with similar results, without the distractions of fuel state or confined landing spaces, but those things definitely contributed and ultimately made the situation worse.

No, simply because we operated with a minimum of a 10% thrust margin whenever possible, especially for high power scenarios like confined areas, mountain flying and any OGE hovering.

You can calculate your thrust margin by looking at the max weight on your OGE graph - for them 2500lbs and reducing that by 10% - ie 250lbs which is 120 lbs lighter than he was at the time of the accident.

His DA was around 1200' given the temp and elevation so he was further up the graph than you imply.

The example in the R44 POH of weight and balance shows full fuel isn't available with 3 POB and a small amount of kit - how much baggage would they have for a fishing trip? And the example uses 170 lbs per pax which is light by anyone's estimation, especially in outdoor gear.

Given the layout of the HLS and the wind direction he should actually have had a reasonably clean airflow, certainly above the treetops even though the report cites mechanical turbulence from the low buildings and the trees (with a max estimated of 20 kts, I feel this is unlikely.

Not sure why you think the yaw induced panic could have happened anywhere on the trip - the proximity of the trees was what seemed to panic him.

That's how YOU operated. Unfortunately, in the world of light helicopters, in order to get any real work done, only loading to 90% of max. gross is usually a dream.

Not at all. If you enter the chart at the 2370lb line, move upwards to where it intersects the 23.6C line (interpolate as required, of course), then across to the left, you will see he can operate at up to a pressure altitude of over 5000ft at 23.6C, i.e. a density altitude of over 7000ft. There is no problem here. Again, he had tons of margin. Not in your book, or the way you fly for the military, but tons in any light helicopter operator's book.

Where are you getting your numbers? Basic empty weight of a Raven II is 1510lb. Full fuel is 287lb. Max. takeoff is 2500lb. That leaves 703lb for people and stuff. Few R44s are that light. Let's say he's got 20lbs of options on board (which is very conservative, it didn't have a lot of options). Call it 683lbs. That's three 200lb guys and 80lbs of cargo. And that's about right, because the only place to put that much stuff is piled on one of the seats. You can't fit it in the stupid little cargo areas under each seat. Again, I'm not seeing any problems here. In fact, this all but proves he was not over gross at any time during the flight unless his cargo was gold bars or him and his passengers were huge, both an unlikely state of affairs.

Agreed!

I'm basing my assessment on the following passage from the report: "When the helicopter cleared the tree tops, it began to slowly yaw to the right. The pilot applied left anti-torque pedal input; however, the helicopter continued to yaw and the yaw rate increased. The pilot then deflected the anti-torque pedals to the right and back to the left several times to check for pedal response while the helicopter continued the right yaw. The pedal inputs did not arrest the right yaw.As the pilot was trying to control the yaw rate, alternating nose-up and nose-down pitch excursions began with increasing amplitude. After at least 2 full rotations to the right the main rotor severed the tail boom as the pitch excursions increased beyond a controllable range."

Any trip is only as good as your planning. Weights, fuel, endurance, weather are the staples of planning and shouldn't reveal any surprises. What seems to have surprised this guy, as a relatively low-time inexperienced pilot, were the planning considerations that are needed to operate safely in and out of a confined area. When you're grizzly and ugly, a confined area is rotor span plus 2 feet. When you are just starting, an open football field can be a confined area. The accompanying aircraft with him got uncomfortable and threw it away, this guy didn't realize he'd run out of ideas until he was over committed to the landing. He was obviously thinking of getting home and maybe what a great fishing trip this had been, instead of thinking what 'gotcha's' were lining up for him. It's a tale as old as time, if you change the plan, change the thinking.

A78, there is no “your world” vs crab’s military world (at least not this time round).

I admire your patience. You are of course 100% right. And crab didn’t read the book.

The MTOW (of 2500 lb) is not a power limit. The power margin is not the difference between the actual weight and MTOW, but between the actual weight and the weight the engine could lift under the current circumstances (disregarding MTOW restrictions). Or as you correctly pointed out, by the difference between the current PA and the OGE ceiling at the current circumstances (which was massive).

The only limit was the pilot’s lack of skill and recency.

Mea Culpa, that's what comes of rushing things when the rugby is on - doh. The example in the POH has 4 POB not 3.

What was I thinking - questioning aa777888?, the font of all Robinson related knowledge:)

Surely he makes a good point?

Taking procedures from (relatively) powerful twin turbine aircraft and applying them to R44s is not a practical or realistic way to operate.

For those earning a living using the aircraft as a tool - probably not, but they are likely to be more experienced and better trained and therefore far more likely to anticipate problems and be better placed to deal with them if they occur..

Those with PPLs and low time would be better served to give themselves as much safety margin as possible.

Operating into confined areas at close to max gross weight is something to be done very carefully and progressively.

Hmm,...that was basically every day training in the R22. :E

Clearly I am talking about proper confined areas like the one in this accident, very limited on space and requiring OGE hover and vertical descent, not just something you have to make a slightly steeper approach into.

So am I :ok:

My PPL(H) training was into a site surrounded by trees, requiring OGE hover and about 100ft vertical descent / ascent to leave. Same site was used on my PPL(H) skills test.

And are you both typical of the PPLH trainees? Do you think all PPLH trainees operate out of such sites?

What is taught regarding performance planning on Robbies regarding confined areas?

Well, I don't know what the "typical" training is, as I am not a CFI.

However, the way I was taught to handle off-airport landings is to crawl it in, basically just riding that vibration down at around 150fpm. So before committing I'd pull it back to pretty much a hover (while still high enough to abort) then check my MAP to see how much I have between what I'm pulling and what my takeoff limit is. If there's at least an inch and a half, or two (depending on just how steep and how high the takeoff will need to be) go for it.

Now I can't speak for other schools, but I went to one of those "CFI Factories" that pumped out CFIs like Tic-Tacs.

That's not performance planning, that's a reasonable technique for confirming the performance you have is sufficient for want you have planned to do.

Hmm,...guess you're right. What can I say, most of my off-airport landings are of the, "hey lets land there" variety.

I'm sure there's some pre-flight performance stuff they taught me, but I'd have to go look for it (think its on my kneeboard), as I haven't actually "planned" to land off-airport since my checkride.

You don't need much - the OGE hover ceiling vs gross weight chart in the POH is the place to start having worked out your pressure altitude and expected gross weight.

You need at least OGE performance and ideally some extra - unfortunately there are no graphs to tell you how much extra you have got.

Hot and High is correct that the MTOW isn't a power limit but taking 5 or 10% off the weight would guarantee you a thrust margin of probably more than you need if the weight line is the first limit you hit rather than the OAT or Pressure altitude.

If you have the performance on the chart then you just need to confirm it before committing to landing - I'm sure you check your hover MAP against the placard to make sure it is correct before transitioning.

Once in the vicinity of the landing area, pull to your calculated max take off MAP - ie your max continuous plus 2.8 to make sure it is available without Nr decay or exceeding any other limits.

One problem is that the OGE graph is based on 5 min take off power and not the max continuous MAP which may pass people by if they are not paying attention - the problem being that if you need 5 min power to achieve OGE, you have no spare to deal with turbulence or any unexpected rate of descent - hence my advice - especially if you are hot and high, to have a thrust margin.

Now a 5% thrust margin was defined in various military Operating Data Manuals (same as POH) as sufficient to overcome light turbulence or manoeuvre gently in the hover - in a couple it quantified a vertical rate of climb of between 100 and 200 ft/min so it is not a huge amount of excess power.

Clearly such advice doesn't exist in the POH but you could experiment to see what difference 1 inch extra MAP gives you from an OGE hover - it will at least give you an idea of the difference between Sea Level at plus 23 degrees and 5300' at plus 23 degrees since the max continuous MAPS are only about 1.4 ins apart from the placard.

R44 Raven II POH is available online from Robinson. Section 5.5 (Performance) contain the graph of weight / OGE Hover, Take-Off power, Nil Wind at Density Altitude.

In addition, relevant to the actual Tread topic, Section 4 contains the checks that should be done after every engine start, and the hover checks - which includes "note MAP"

Craab - you make a good point. Don't recall being taught in PPL lessons "performance planning" for the confined area flight we were going to undertake. General planning for a flight (weight & balance, performance, fuel, route and diversions, etc) but not specifically planning ahead for this. Certainly was taught - as Robbie notes - how to assess the site, check available power for OGE and descent / climb-out, and how to approach and get into the site. That is not the same thing, as you say. There is therefore room for a training improvement there.

Training did include "artifically lowered" power so that you had to decide not to go in, or once in artificially lowered margins to show what might happen you now had to get out with less power than you might have wanted. This included towering but also restrictions so tight that you could not get out - as a means to showing you how to take responsibility for stopping and rethinking, rather than pressing on until you hit a tree.

I thought (still do) that the technical training was good and it left me with with this. The site we used in training for confined area was very (by my standards) tight. When first shown it from above, my reaction was "I appreciate the skills and training, but I am never going into a site like that when I have my license". I have stuck to that decision ever since, and take the view that "just because I can" doesn't mean that I should. There is, in reality, no justification for me to act otherwise as I only fly for pleasure. I do use these techniques - icluding OGE hover and descent into a lawn surrounded by Scots Pine trees, but the space is more than 3x larger than my old training area.

I would add; some years after getting my PPL the airfield stopped the use of that confined site and instead provided one surrounded by low bushes & shrubs and actually open on one side. Nothing like as challenging, and though technically "safer" to learn in I don't think it provides as good a training experience. Doing annual LPCs at that field, using that site is pretty much a non-event to me, and I think the risk is that you don't see the value of making all the right checks and asking the right questions as then you land on something that is "less difficult" than some of the Heli Pads provided on the airfield (close buildings giving recirculation issues, for example).

Exactly right.

Those margins simply don't exist in the real world of Robinson helicopter operations. R22 useful load is 490lb. With two 170lb people inside that's less than full tanks, or less than two hours endurance. Raven II useful load is already discussed below and is equally challenging with 4 people and stuff on board and a desire to get real work done. If you are in a Raven I, or a fat pig of an R44 like a Clipper II (aka Raven II with pop-outs) with air conditioning, now you have lost 100lbs of useful load. The bottom line is that these machines are nearly always flying at near max. gross when full.

The only time you have the sort of margin you are talking about is when you are flying an R44 with only two people on board (or an R22 with one). If you want a "rocket ship", two people and half tanks. And the performance difference is dramatic. That makes for safer initial training, but ultimately one must learn to fly the machine the way it will really be used, and that means at max. weight. In the R22 that happens by default. In the R44, at least at the school I attend, that happens by finding two other erstwhile individuals to fill the back seats and endure max. performance takeoffs, confined space landings, and ham handed auto's without puking (screaming is allowed). Normally these are more students and it's actually quite a bit of fun as each student rotates through the pilot's seat. The repartee meter does get pegged!

Robinson marketed the R44 Cadet to address this issue, but it's just such a dumb choice on so many levels. Few small schools will buy one because they need a machine they can use for more than just training. And it actually offers too much performance and does not prepare one for the real world of a regular 44 loaded to the gills.

If you mean check your hover power vs. the 5-minute max. on the placard, of course. That is (should be) taught and is a no-brainer. It's generally taught that if you've got 2" MP below 5 minute max. you can make a max. performance takeoff. This was well and thoroughly taught to me, with innumerable exercises involving artificial power limits. During my private and commercial training there was a lot of emphasis placed on "making it out safely", including such things as shuttling partial loads to a spot where a max. perf. was not necessary and other techniques.

Actually the landing power check, if you even need one (you did plan it, right?), is generally as follows: assume level flight 500ft above the landing altitude at Vy, then see if you've got 6 or 8" of MP margin (depending on who you talk to) against 5 minute power (don't forget to check OAT, pressure altitude and the placard!) If you do then you are probably OK for OGE hover. This is poorly taught in my experience. At least it was where I learned. We did spend a lot of time exploring the lack of OGE hover using artificial power limits in a run-on landing environment, but never for spot landings, which I felt was an unfortunate hole in the instructional repertoire. I have since developed that experience after the commercial check-ride, but I feel it should have been sooner. In the school's defense it can be difficult to train if you don't live in a hot/high environment, and the potential for a training accident is high.

Welcome to the wonderful world of very light helicopters where those margins are razor thin if they exist at all.

Again we have the rules of thumb for MP margins as discussed above, that are admittedly not in the POH, to go by. They have proven themselves over the many decades that Robinson helicopters have been in service.

Regarding confined space operations: I can't speak to other schools. The school I use is a pretty good school in this regard. Like any school they are obviously focused on getting people to pass the FAA checkride. But they will train you just as hard and thoroughly as you can safely be trained. Not every student learns at the same rate, not every student wants to be an accomplished helicopter pilot (e.g. wealthy guy in a hurry--just make me good enough--one major reason for the Robinson accident rate). But for folks who have the drive to train more comprehensively, this place will take you way, way beyond paved runway to paved runway and Farmer Jone's field. During my commercial training surprise landings were as common as surprise auto's. Instructor says "See that hole? Put me in there. See that pinnacle? Put me on top." One of the more challenging sites is a mountaintop transmitter site that is very popular with the instructors. It's a forest of guy wires and tall pine trees and a 15ft square gravel pad on a jaunty slope. Really great stuff.

One does see quite a bit of this sort of thing on the schools who like to publish on Youtube. Mischa Gelb's stuff, for example. One would like to think that all schools are teaching the same stuff to the same level, but of course that is not true.

So you'll be able to tell me what extra performance 1.4 inches of MAP gives you in an OGE hover then?

Give me a procedure to follow and maybe I can make that measurement.