Moggy’s Tunaboat Helicopter Manual Ch.3-C “Take-Off “
Posted on August 1, 2009
Bell 47, a classic work horse
PART 3 “Moggy’s Tuna Manual ” “Handling your helicopter “
Chapter 3-C TAKE-OFF
You may hear it said that -where Tuna boats are concerned- there are more take-off accidents than landing accidents. If you include all the really unpleasant (and usually fatal) tie-down accidents (see next chapter), then I suspect that’s true. You might not expect that. The closest I’ve come to ‘splashing out’ was on take-off, not during a landing.
How-ever… let’s pause here, and remind you that there are plenty of landing accidents! So what does that say for the Tuna helicopter industry’s safety record?
It’s always interesting to chat with former Vietnam pilots who have also been tuna flying.. These guys are amazing, have endless stories, and when that generation finally is gone, the helicopter industry will never -ever- be the same again. We will never have such a crop of incredibly experienced pilots again. And we’ll never…. quite have the same freedom loving, swashbuckling, independent, crazy, fun-loving Hell’s Angels in the helicopter industry again. You should ask one of these guys the question, as to how the accident rate in the Tuna helicopter industry compares to Vietnam! You might be surprised. I have heard these guys comment, many a time, that for an “Ash and Trash ” (non-combat) helicopter operation, that tuna flying was just as hazardous as their old flying in Vietnam.
Some would say more so…
Back to the tuna boat take-off.
Firstly, there is a certain type of pilot who is obsessed with going up off the helideck. One such worthy managed to hit his tail rotor off the crow’s nest. Think how high the crow’s nest is above the helideck! Thirty feet? His ship was underway, and whilst he went vertically upwards, the ship moved along underneath him, the crow’s nest clobbered the tail rotor. The sequel is kind of unique. The pilot entered autorotation, and landed back on the helideck! He maintains he planned it that way, but everybody else says:
“Pfffffffff! Dumb luck! ” Whatever…
I was on a ship where the previous pilot and the captain had been arguing over this precise issue. The captain complained to me that he kept instinctively ducking in the crow’s nest. He was worried, and unhappy about it. Their relationship broke down, and the pilot only did one trip and quit.
This vertical obsession seems to be quite common, but I think most tuna heads will unhesitatingly agree that the most important consideration is to get clear of the ship. And in a manner that puts you in the best possible situation to cope adequately with worst case scenarios. Regardless of helicopter type, it’s nice to get well away from all those aerials and radar domes. Your ‘deck edge crossing time‘ (DECT) needs to be as short as reasonably possible. There is (especially for single engine machines) a nasty ‘red zone’ where you are (in the event of a sudden power failure) unable to land back on the helideck, and probably unable to avoid smacking your tail rotor off the deck edge. Nasty!
It follows that you really don’t want to waffle about, and cross the ‘red zone’ at a snail’s pace, whilst putting all your effort into climbing vertically! On the North Sea, off the oil platforms there, the last thing we did was to take off into a four foot hover, and then sort of waffle over the edge of the helideck on our merry way! We would climb (twin engine) to a twenty foot hover, pitch the nose down ten degrees quite abruptly, and go like hell! Thinking worst case scenarios, if the engine quit before we went for it, then we landed back down single engine. (interesting training, especially at night!) But once we pushed forward… you were not going to land back. You kind of held your breath for a few seconds, and breathed deeply when you were clear.
The story goes that one machine was coming off the North Alwynn, which is like a huge five story hotel stuck in the middle of this cold and inhospitable sea, some 230 miles east-north-east of Aberdeen. Just after the pilot had pitched the nose down and committed himself, one of the two turbines failed catastrophically. The result was utter chaos and commotion lower down in the galley, where all the diners saw was the underside of a Super Puma heading rapidly down to the sea. In fact… everything was -more or less- nicely under control. The Super Puma can’t hover on one engine, but she sure can fly away once you have achieved translational lift. In this case, a well thought out take off profile and good training beforehand saved the day. That’s a story I got first hand from the captain who flew it. And recently here in the Gulf of Mexico, in 2009, a Sikorsky 76 crew had an engine failure at the worst possible moment coming off a platform. They did everything right, and got to fly back to their base with one engine and one helluva good bar story. The interesting thing for me was to hear the story from the first officer. Here was a pilot whose eyes, in telling the story, conveyed the intensity of the experience. I guess that made a believer out of him, as far as the value of training, training, training is concerned!
At first sight, these incidents might be taken to vindicate those who would try and gain height vertically off a tuna boat first, before moving away. But hang on!
1) I don’t know any twin engine helicopters operating off tuna boats.
2) The average North Sea platform is bolted firmly to the seabed, or, in the case of a semi-sub, is moored firmly to the seabed. These mammoth piles of steel and concrete are not punching along at anywhere from 12 to 18 knots!
Also, these platforms by and large are ‘humongous’. You usually have a much, much, much greater rotor tip clearance from obstacles than on a tuna boat. True, there are some really big tuna ships, where you could land three or four little R-22’s. But on many tuna tubs… I flew a Bell 47 off a deck where, if you touched the blade tip with one hand, you could just about touch the Immarsat dome with the other! If that doesn’t impress you, try and imagine a nice, juicy, stormy, rain lashed, rock-and-roll day for your final approach. It impressed me! This is really not the place to start going up to twenty foot hovers vertically over the helideck. There is a veritable forest of aerials behind the helideck, and the crow’s mast behind that little lot. What I do, on any helicopter, is (after the thumbs up from my helper, indicating that the belly hook is clear, and all appears to be okay) is to ‘gently increase’ collective until I’m really light. I make sure I have neutralized all movement, sideways or otherwise. (see Note 1) I may be carrying quite a lot of right (into-wind) cyclic. A little bit more, and we’re hovering at three to six inches. I maintain my position on the deck just for an instant, check all systems okay, controls responding normally….. then another smooth increase in collective up to maybe two or three feet in a Bell 47, maybe… four feet max, and then, just like a Puma, nose down and go like hell! I cross the ‘red zone’ as fast as I can, the shortest DECT I can manage, and now a bit of forward cyclic down towards the sea. The forward cyclic helps speed me up away from the ship, and the smooth dive towards the sea helps me reach translational lift quicker, gives me a chance to lower the collective lever a fraction if (which is likely in a Bell 47) my rotor rpm is beginning to decay, and also…. raises the tail!
I am now also well situated that if my rotor rpm (Nr) has really taken a dive, I can continue the descent towards the sea, speeding up all the time. And if necessary, I can continue all the way down to four feet, at which stage ground effect (yes, above the sea it also exists!) would also help save the day if I’d really screwed up on the rotor rpm.
Two up, with full fuel, in a Bell 47, I don’t muck about trying to climb vertically much above three feet above the deck. You’ll be running ‘out of puff’ soon, and if you do get higher, it will probably be at the expense of rotor rpm.
Robinson R-44 A good bird in the hands of a respectful pilot
Huh! You might say. Sounds a bit rushed and bothered to me. Well, yes it is in a way. There’s a lot that could conceivably go wrong, at the worst possible moment. I often wonder what percentage of pilots fly defensively, assuming the worst is going to happen at the worst time, and are -actually- pretty damn ready to deal with it. And what percentage of pilots kind of get…. too comfortable. And who are just not ready, able, pre-disposed, gung-ho, trigger happy, to DEAL with sh…. coming their way. I think it really is an ‘attitude of mind’. Defensive flying, ‘suspicious flying’, the what-kind-of-gremlin am I gonna NOT LET BITE ME today sort of flying… That is what I advocate, with a passion. And probably, if I was to be honest, because I’ve come soooooo…. close to getting really, really, wet, flustered, and embarrassed.
In putting together this manual, I’m determined to be as honest as I can. If I come across as a superior aviator, with a flawless record, a pillar of wisdom, and well placed to sit in judgment of lesser mortals, (the ragged, unwashed masses), then it’s probably high time I tell one of the many tales I could tell, against myself. This isn’t a ritualistic self flagellation, like those medieval monks who were determined to get into heaven by beating themselves red raw with knotted lashes. It’s just more a practical admission that we all make mistakes. None of us can ever hope to survive, if we are going to make every mistake there is to be made, one at a time, and then draw our lessons from it, and move on.
In the helicopter industry, we’d be dead in no time.
It is imperative to learn from the mistakes of others, eat humble pie, admit that it could well happen to us, and move forward, cautiously. Helicopter flying is wonderful, about the most satisfying and exciting thing I’ve ever done, almost as good as sex; although… given a choice between forty virgins and a gleaming Hughes 500….hmmmmmm. Gimme the Hughes. (imagine forty women cackling on about last night’s….no!)
So there I was, on my third ever take-off from a tuna boat. In a Bell 47, with a tired old Lycoming O-435 engine.
I came up to a nice hover, three feet or so, and then, feeling all nice and relaxed, set out off the deck. I flew out horizontally, without a slight dive. Whether or not I hadn’t wound open the throttle properly, or what I did, I don’t quite know. But the moment I lost ground effect from the helideck, the moment I was starting to move out over the sea, the rotor rpm decayed so fast that I started to sort of mush out of the sky. The sheer speed at which it all went from normal to ‘pear shaped’ really surprised me. I had the presence of mind to shove the cyclic forward, and this raised the tail which – I was told this later – was never in danger of striking the deck edge. Down we sank, horribly, with the rotor rpm somewhere about 270 if I remember, until, just as I thought we were going to crash, (at this stage I had leveled the floats, and was preparing for impact) all of a sudden… the ship magically arrested our descent. Good old ‘ground effect’ had come into play, and this had rescued the day. The invisible ground cushion, and the friend of pilots. I flew away thinking I had not touched the water, but I was afterwards told the right rear float had ‘kissed’ a wave!
Close! It’s hard to describe that hollow feeling in your stomach, when you think for a second that you’re about to ‘go in’.
The concept of ground effect over the waves gets some guys all uptight, and some will even say there is no such thing.
You will hear some pretty esoteric theories about all this.
All that ‘ground effect’ is about, is that the presence of a surface breaks up the vortex from the rotor. The presence of ground (or sea), reduces the re-circulation of turbulent (used) air through the rotor disc.
So do you get ground effect over the sea? Yes! Sure.
So a Bell 47 tuna pilot, or an R-22 pilot, who feels he is getting into trouble with his rotor rpm or his HOGE, does well indeed to make a determined, positive move to head for the ‘safety’ of that invisible ‘ground cushion’ over the sea!
Whilst herding in a Bell 47, and with all the twisting and turning, I would often dip on down, just to let the rotor rpm build back up. You get used to it, and it becomes second nature. Just remember those rolling waves coming through, aiming hungrily for your tail rotor. Many, many a tuna pilot has flipped over by allowing a wave to contact his tail rotor blade.
Any good helicopter pilot, when he (or she) is near the surface, is constantly thinking where his tail rotor is, in the horizontal plane (turning), and in the vertical plane (pulling back on the stick).
Don’t you LOVE a Hughes 500! Such a wonderful, wonderful helicopter. After a Robinson R-22 or R-44, or a Bell 47, although these are good, good birds, the Hughes 500…. will bring a smile to your face. Such a pleasure to fly.
A Hughes 500 – every tuna helicopter pilot’s dream machine
It makes your take-off so much easier, because of all that nice extra ‘oomph’. I might come up a little higher, but I still apply forward cyclic quite positively, and I still ‘go like hell’ to minimize DECT and get through the ‘red zone’. The big difference with the Bell 47 or the Robinson is that you’ve got sooooooo much more power, with that lovely Allison C20B engine. You can make a positive departure, positive stick forward, positive ‘get the hell away from the deck’, and STILL climb at the same time. You must think aggressively about getting away from the ship. And be prepared to NOT be surprised if something quits. If there is a sudden deafening sound of silence (ignoring your observer’s screams), at the worst possible moment, accept it, deal with it, go for the water. And if you are swopping between a Hughes 500 and a Bell 47 or a Robinson, remember the Hughes 500 requires nimble feet. That boom is shorter, so it’s ‘short coupled’.
If you go from a Hughes 500 to a Bell 47 or a Robinson R-44, you must pay big time attention to the fact that you now have a longer tail boom. A modest flare over water (or the deck) that is maybe not going to hurt you in a Hughes 500 (think tail rotor), is really going to hurt you big-time in a Robinson R-44 or a Bell 47. I cannot over-emphasize, here and elsewhere, the importance of guarding your tail rotor, thinking about your tail rotor, and being aware of just exactly how many (hundreds and hundreds of) accidents there have been on helicopters, where the pilot’s failure to ‘think tail rotor’, was the primary accident cause.
Muggins here, the great expert, the writer of the Tuna Manual, fount of all knowledge, made a complete fool of himself another time as well, in a Bell 47. It wasn’t quite as dramatic this time, but still upsetting. It hurt my pride, for I should have known better. The net was out, and I was trying to take off from a sloping deck. It was sloping pretty good. However, it was a relatively calm sea, a nice sunny day, and I was feeling pretty relaxed. With the sea pretty calm, there wasn’t that horrible rolling going on, with the deck moving about and being a damn nuisance. That’s when you most need to worry about a tail rotor strike -if you’re not careful- and be on guard. But this was a pleasant day, no wind, hot, and a tail rotor strike off the deck was not high on my list of worries. I got into a hover all right, with the rear of my floats six to twelve inches above the deck, and the front rising up higher than that. Quite a lot higher. Maybe four to five feet.
All of a sudden, I just felt I was ‘out of puff’ already. As I moved forward, the rotor rpm (Nr) started to decay, and it all felt horrible. By now I was a little more experienced though, so I knew better than to hesitate, and commence a lengthy inner consultation as to what the fufufu was going on… I just nosed over and skooted off on a downward profile, easing down on the collective lever as much as possible to get the Nr back.
I figured out -thirty seconds too late!- that various factors had aligned themselves against me, and that I had been too damn cocky to take it all into appreciation.
1) No wind….
3) Steeply sloping deck…
The steeply sloping deck simply was the killer. It just meant that my ground effect was being reduced. Or, if you like, my ground cushion was being adversely affected. The moment I moved forward, the deck was rapidly falling away below me. Although I was technically still ‘over the deck’ it had the same effect as when you push out over the edge of the helideck. The vortex was building up over the front of the disc. So there’s another trap for the unwary!
I really should have been a bit sharper that day. I had just spent a boatload of hours instructing students in Robinson R-22’s. A really nice machine. Part of that training was always a demonstration I gave of slope take-offs, and the reduced ground effect associated with it.
Finally, there’s a classic true story about an accident involving an Enstrom helicopter, on a commercial flight, trying to take off from Battersea heliport, on the banks of the river Thames, London. The Helicopter Commercial Pilot had two passengers and their luggage. He could barely hover, but he thought about it, and reckoned that if he took a ‘run’ at the edge of the dock, that he’d be able to sail out over the Thames river. Hey-ho! Off he went, taking a determined run at the edge. Out he sailed over the waters… well and truly ‘committed’…
Loss of ground effect before achieving translational lift! Everybody wet and flustered!
One Enstrom Helicopter written off.
(And there, but for the grace of God….!?)
Note 1: “Helicopter Aerodynamics ” by R.W.Prouty has a section written purposefully for Tuna Helicopter Pilots.
It even mentions the “rolling deck ” problem!
It’s on page 220, and I strongly recommend you buy the book and look it up. The paragraph is entitled:
“Dynamic Rollover “…
Last edited by Francis Meyrick on September 28, 2009, 7:34 am