s-58 aerobatics

[TheMonk]

Did a search but came up empty, so here' goes.

S-58 display by Royal Thai Airforce or Navy pilot I believe.

YouTube - the best helicopter aerobatic of this world (http://www.youtube.com/watch?v=s4xZIg6NNkw)

[SASless]

S-58T actually....probably former Air America aircraft if I had to guess.

To address the old question....Huey or 58T?

Try that in your Huey!:uhoh:

[TheMonk]

SASless:S-58T actually....probably former Air America aircraft if I had to guess.

Yes, S-58T for sure.

I don't think Air America had any S-58Ts though, but I could be wrong.

[soggyboxers]

I'm sure SAS will remember when Bristow removed the bifilars from their S8Ts in Teeside to reduce weight so they could operate with a payload/range combination for which the 58 was never really designed. I forget the crew now who were IMC and picked up a lot of icing on the jacks, but think that at one stage they may have looped! They recovered when they broke cloud at just under 1,000 feet with an extreme nose down attitude. I believe a couple of the pitch change rods were actually found to be deformed after they landed. Maybe someone who was there at the time will recall the exact details?

Air America leased 6 S58Ts in Laos, but 3 were listed as downed in 1973 and the remaining 3 scrapped in 1974. The Thai Am company modified 18 Sikorsky S34 Choctaws to S58Ts for the Royal Thai Air Force from 1978:

http://farm4.static.flickr.com/3242/2620388533_8a36e0557f.jpg?v=0

[Dan Reno]

Thailand used these helos afterwards for a fishing reef: Phuket's Sky Coral Reef: A Photo Celebration - Phuket Wan (http://phuketwan.com/entertainment/phuket-aircraft-coral-reef-skydive-squadron/)

[SASless]

Soggy,

That was DE, Rip Pearson and I believe Brian Oxley that did the IMC inverted....air medals hanging in his face deal.

Must have been fun in the dark....as it happened at night as I recall too.

The only damage found was the lower PC links attach points which had nice big Sikorsky Iron Works lugs around them...were beat to heck (the lugs). DE was put into the hangar for a bit and some serious changing of bits was done as I recall.

The downstairs guy suggested he knew he was in trouble when he found himself walking about on the ceiling.

If it was not the Ox...it might have been "Dave"...last name escapes me now

I loved flying with the Ox....all he ate was the boiled ham sammies....and he would pass up the crabmeat, shrimp, smoked salmon fare to me. If he ever finds out how many tiimes I ordered up the smoked salmon....well he might just snap my neck for me.

[bast0n]

Ah the glories of keeping on positive G with no danger of a mast strike...........

Great bit of flying - I wish I had that amount of nerve, especially at such a low height!

[ShyTorque]

The Alcock turn - looks like a loop but it's not (someone left a comment below and obviously thought it was looping). :ok:

Unlikely to get a mast strike with that type of rotor system.

[bast0n]

Yup - note that I said "no danger of a mast strike"!- Referring to earlier remarks about trying it in Huey.................... As you say it looks like a loop but is not - but pretty damned close, and filmed from the right angle is most impressive. We tried similar things in the Wessex 5 but I don't think we got as daring as this chap..........but then again we were strapped to it and the view from inside was a bit minimal.

[ramen noodles]

I've flown a bunch of those loop-wing overs in demos and shows. Done right (with the tail to the crowd) the thing looks great, but it is really about a 135 degree bank, done from 50 degrees nose up. Basically an off-axis loop, perhaps 45 degrees from pure vertical.

The 58 looks ok in the maneuver, but the S76 looks like a P51 when you flash by at 160 and then climb into that maneuver. Flip it over as you decel thru 60 knots and the tight little circle at the top is most impressive. Worst place is the fly down - never hold the nose low for long, the speed you build is what make the earth rise up too fast..

[ShyTorque]

but the S76 looks like a P51 when you flash by at 160

I thought Vne was 155 kts? :oh:

[SASless]

Shy as anyone knows the Vne of the 76 was bogus.....as it was set primarily on the limitations of the PBA actuator or whatever it was called and the fact Sikorsky did not want to spend a lot more time and money getting another ten knots or so for certification pruposes.

Perhaps Nick Lappos can explain that to us again....as he has done a few times over the year.

Just as in the S-58T....with a bit of finesse....one can overtake a Puma in the old T-Bird given a chance.

The radio chat enroute to the Ekofisk one morning was...."I say chappie....is that not an S-58T?" ....as I pulled by with about a ten knot advantage....to which I replied...."Nope.....it is a 58GT!":O

One could say real Vne is when the nose begins to pitch up and roll left due to blade stall in left turning rotor systems.:E

[ShyTorque]

Shy as anyone knows the Vne of the 76 was bogus

I'm very aware of what's been said unofficially but I'm surprised at your comments. Nick was test flying the aircraft, we aren't. Neither is the pilot who flies the aircraft after a limit has been bust and nothing recorded in the tech log.

Surely you aren't of the opinion that RFM published limits are there for "less knowledgable" pilots' guidance only? The manufacturer bases the maintenance schedules (and the warranty) on the assumption that the published RFM limits are being adhered to. The insurance company will also assume that the published RFM limits are adhered to.

[bast0n]

SASless - gosh you bring back memories!! VNE measured by pitch up and left roll..............Brilliant! I remember in a Whirlwind 7 as SAR Culdrose in a howling westerly gale going low over the cliff edge as fast as we could to rescue some swept off his feet fisherman, hitting retreating blade stall par excellance as the angle of attack dramatically changed due to the rising air at the cliff edge. WW7 flipped nose up, flicked left, crewmen thrown from door to somewhere else, intercom unplugged, hero pilot fleetingly thought ******me, and once through the updraught the WW recovered itself. Only thing left to do was to get the RRPM somewhere back to where the makers thought that onward flight and heroic rescue became possible. I learned a little more about flying from that, and thank goodness it was a tall cliff to allow recovery before hitting the salty stuff. Keep going SASless, you bring a breath of fresh air to these proceedings...............

[ShyTorque]

Seen that myself. My instructor (RIP, Ned, a motorcycle accident took him shortly afterwards) dived our Whirlwind 10 from 500 feet running in for a turning quickstop at the relief landing ground (Chetwynd). At about 50 feet agl, while pulling the aircraft round in a very steep right turn, he hit RBS. Thankfully for us it was a right turn. The aircraft shuddered then rolled very rapidly left as advertised and left us beyond upright. If we had been in a left turn I'm sure we would have gone inverted and I might have been held to blame as the BOI would have assumed the student was flying. No fire cover or ATC at that airfield... Both of us learned from it. Ned apologised.

[SASless]

Shy,

You ever consider that there is more to life than thirty miles to the gallon?

Airspeed indicators can be off by a knot....gusts and turbulence can bounce the needle about a bit....some silly sod might just throw a number out there in telling a good story....heck...there might even be a bit of tolerance thrown into the calculation of the very number itself.

I did not state one should ever knowingly exceed Vne....read the post again closely laddy.

That being said....every now then in flying....putting down the RFM, AIP, FAR's, and all that hodge podge of bulletins, notices, edicts, decrees and the like....and just flying the aircraft for the sheer pleasure of it.... is what separates real pilots from the cook book variety.

Until you get out there and pull a few G's and feel the aircraft load up and get to shuddering....or point the nose in directions beyond dead level....or zip along a few feet above the ground at warp speed....why Man your soul just hasn't lived.

I am not suggesting you overstress the aircraft or input any abrupt loads on the old girls....but rather get to really handling the thing and "feel" the aircraft. You can do it...do it safely....do it within the most the rules...and be the better for it without hurting anybody or anything.

Sheeeee-It Doc! Flying is supposed to be as much fun as one can have with your pants on! (Skirts down for Fair Whirls and you Jocks out there!)

If you do not push the the edges a bit then you forget where they are as they get all fuzzy. Maybe I do not see the limitations as being etched in steel but rather inked on a page where the line blurs just a tiny bit.

I can think of a hand full of occurrences where with a lot of outside help and some timely divine intervention I have tried to tear the blades off a couple of aircraft and gave it the old college try in doing so....and nothing got damaged despite my best efforts..Perhaps I think more of the strength of the aircraft than I should.

A final thought....I can assure you RBS is the ultimate Vne....you will not exceed that speed (granted that speed will vary upon the conditions).

[ShyTorque]

SASless, back to using your old technique again, i.e, patronisation in an attempt to recover an argument. I might be a mere "laddy" in your eyes but I've done a little, too, albeit only over thirty years of doing it for a crust.
The previous poster to you appeared to write that he advocated running in at a speed beyond Vne. I questioned that and you jumped in. :rolleyes:

As far as "fun" flying goes, my previously officially sanctioned display was banned by the hierarchy after two other pilots flying the same manoeuvres in later display seasons had a problem. Each took part of a tail rotor blade off against the pylon, something that wasn't possible unless the blades went beyond the mechanical limit of the hinges. About ten inches beyond.

If "lsh" reads this, he might tell us more about that - he was crewman in one of the two aircraft that suffered the tail blade strike. "Jellycopter" recently reminded me that I showed him a watered down version of the display when he was my student and we were out doing "sloping ground" in the local area. He has obviously some recall of it.

We took it further than the S-58s in the video; in retrospect it was a little too far. In order to get the vertical performance we needed after our run in at just below Vne (we flew to 85 degrees nose up to 450 feet agl) I used to cyclic pull until the collective pitch gauge needle vibrated then back off, just a little. God knows what it did to the transmission and pitch links; I would never do that to an aircraft now because I know better.

One day during a work-up practice I cavitated both hydraulic systems at 400 feet agl with 90 degrees nose down (actually my crewman told me we went almost 130* nose down during that one). This was in a seven tonne aircraft. The cyclic kicked hard then locked for a couple of heart stopping moments. I learned a little more about respect for the limitations of my aircraft from that.

After my display season was over, a routine engine change on my regular aircraft was needed. The ground crew chief told me that it came out of its mounts with a little jump. They couldn't get another engine back in. Something was pulled out of line. It was the barbeque plate. I learned more about mechanical sympathy that day, too.

These days I admit I've calmed down more than a little, having had more than my fair share of fun and sometimes exploratory flying, out of respect for A) the very fast little twin which does it's evil best to go well beyond Vne at any small opportunity (even straight and level, whereupon it logs an exceedance in it's computer brain, for the engineering department to see) and B) for the owner sitting in the cabin who pays my salary.

[ramen noodles]

Shy said, "These days I admit I've calmed down more than a little....."

Haven't we all!

And yes, 155 is the Vne, but when the helo is experimental, the engineering limits are the ones to follow.

[Fareastdriver]

feel the aircraft load up and get to shuddering....

Sounds simple until you know what loads are being put on the rotor head at that stage. During the development of the Puma they were regularly flown beyond 200 kts and sustained operations at 300 Rrpm. The classic was VNE at max aft C of G and putting the yaw channel into open loop, wait two seconds and recover from the inverted. The stacks of discarded rotor heads and gearboxes in the Aerospatial hangar were the accepted casualties.

get out there and pull a few G's

The only limit I can remember was the early 330G manual that had 2.67G below 6400kgs. A sustained level turn at sixty degrees of bank is about 2Gs. To do this you have to have a light aircraft with a lot of reserve power flown at VBROC. Outside those parameters you are overstressing the head. That’s why they have bank limits at high AUWs.

Years ago a fellow pilot decided that the Whirlwind VNE wasn’t fast enough for him. He cranked the collective up to Max Con on the engine and accepted the speed. Being the only one up top nobody knew until he inadvertently passed his flight commander with his extra 15 knots. When the truth came out they had no choice but to change all the rotor heads on all the aircraft he had flown on the squadron.

Blade slaps on the pylon. It is a five-bladed propeller that is capable of pulling a five ton fixed wing along at 170kts. It is incredibly powerful, that’s why there are all those doubling plates on the Pumas pylon/boom joint which is not helped by pilots trying to twist the pylon off when they are taxiing it.

Helicopters are blind, that’s why they keep flying into mountains. As long as they are in balanced flight, correct Rrpm and reasonable positive G than they do not know which way up they are. Keeping within those parameters you can do most things except make it talk. It is when you go outside those parameters that the trouble starts.

The classic Torque Turn. You cannot do it with a governed turbine helicopter. That is the prerogative of a ungoverned piston version. Especially the Sycamore which had insufficient cyclic of yaw authority so cranking the throttle was the only choice. On turbines pilots tend do fly it like a fixed wing stall turn. Unfortunately there are at least two vastly different parameters. The first is the rate of which the airspeed decays. Fixed wing have a nice engine which is pulling them up, helicopters don’t, so that plus gravity means they airspeed drops like a stone. As it passes through 45kts you have about two seconds before it is zero. A bootfull of pedal turns it, great, but if you are not fast enough two seconds later it can falling at 45knots, sideways. A fixed wing doesn’t worry, the fin assembly can cope with this without stress. But on a Puma going to the right you have full pedal pushing the tail rotor towards the airframe and as you are outside the sideways flight limit of the aircraft, the blades bump off the pylon.

Helicopter fuel and hydraulic systems are not designed with aerobatics in mind. The Puma is not so bad as the engines use tanks that are continuously topped up. Other types are not the same. Taking the S76 at a low fuel state, vertical operations can cause the fuel to bank up against the wall of the tank and uncover the fuel feed. Turbine engines, glow plugs or not, do not like slugs of air and pointing vertically downwards at 300ft is not the best place to initiate an EOL. The same with hydraulics, especially large capacity systems like the Puma.

In any form of inverted flight it is obvious that under positive G the main rotor is assisting gravity and in a very short time you will have insufficient roll rate to return the aircraft upright before hitting the ground. Fixed wing can reduce or apply negative G to extend this time. Helicopters don’t like this, even more as the droop stops are out.

One must always remember that if you do horse about with a helicopter, without regard to the stresses, that when you sign it off as serviceable the subsequent pilots and passengers who get into it do so with the belief that it IS fully serviceable. Who knows, when something eventually breaks, it may well be you in it.

Sasless is right in one way. There is no point in being a pilot if you cannot throw it around a bit to get away from the mundane routine. I do it still, although I should be old enough to know better. There was no shortage of Chinese co-pilots who want to come along with me on an air test. The primary rule is that there should be NO signs of protest from the aircraft. With this in mind you can go ahead and if you are the main attraction in a ball of fire and pillar of smoke on the airfield you can be comforted in knowing that the aircraft was fully serviceable when it crashed.

[ramen noodles]

fareastdriver,
Your post is filled with inaccuracies and semi-mythological technical fact to be of little use.
Some examples:
Helicopter fuel and hydraulic systems are not designed with aerobatics in mind.
The gravity fed hydraulics of Puma have no resemblance to the pressure feed hydraulics of an S76. One is unsuitable for aerobatics, the other is. You think hard about which is which.

The only limit I can remember was the early 330G manual that had 2.67G below 6400kgs
That limit is due to static structure, a kind of proof loading of the fuselage, and has literally nothing to do with the rotor and its propensity to stall at far, far lower load factor.
The classic was VNE at max aft C of G and putting the yaw channel into open loop, wait two seconds and recover from the inverted
Precisely who are you kidding? Yaw hardovers and inverted recoveries! give it a rest.
In any form of inverted flight it is obvious that under positive G the main rotor is assisting gravity and in a very short time you will have insufficient roll rate to return the aircraft upright before hitting the ground.
I'd suggest a short course in how a helicopter is controlled, the last one didn't stick.

The above fit of pique now excised, your advice to care for the machine so as to protect the others who fly it later are spot on.

[TheMonk]

soggy

Air America leased 6 S58Ts in Laos, but 3 were listed as downed in 1973 and the remaining 3 scrapped in 1974. The Thai Am company modified 18 Sikorsky S34 Choctaws to S58Ts for the Royal Thai Air Force from 1978:

So they did have them. Thanks for that fact.

I only remember seeing the ones with the clamshell doors with a hughe radial engine in them. No "snout" on the ones I've seen in Laos.

[Lt.Fubar]

I do realize that S-58T were never actually build - all were Twin-Pack modifications of piston Choctaw... though the type was registered as such, so how come there are no RFMs available anywhere for them? Not on paper, not in electronic media... not for sale, not for free download ?

What were people flying them using, if nothing can be found today ?