Yes a helicopter can fly with one blade missing.

However, it requires a special rotor.

The swashplate must be replaced with a swishplate, plus the normal blades must be replaced with gay blades.
The swishplate has the ability to control gay blades as they continually depart and return to the 'group'.

The Bristow S76 that crashed off Yarmouth lost about 12 feet of one blade.

The head and main transmission were torn out of the airframe.

There is a full report on the AAIB website.

For the record that was the second Bristow 76 to loose a blade, the previous aircraft accident was caused by spindle failure again not survivable.

I also read about an OH6A pilot who got shot in a blade and had to land behind enemy lines. After removing the opposite blade (leaving two from four) and stripping the machine bare he managed to get it airborne and stagger back across to safety, have no idea where I read it and I have tried to find it a few times...Is it in "tales of a helicopter pilot"??

SL

As Mr. Dave Jackson should be aware, a rigid rotor configuration would be more survivable than a hinged rotor configuration in a blade-off condition.

Right?:ok:

I flew chase for those flights, back in the day. Same config, one shot is from below, so the rotation appears backward.

The 3 bladed flights were flown to confirm the behavior of the rotor at lower blade loadings, so that performance for the next gen of Sikorsky helos could be examined. The ability to recover was also tested, of course, but at the cost of flight test, that was not the biggest driver.

The vibrations were simply awful, BTW. The normal 53 needs no vibration suppression gear, but since vibes go up when number of blades go down, the three-bladed 53 was another world. The pilots (Jim Kay and Al King) had difficulty reading the instrument panel.

I think what cross-land is trying to point out is that the rotor blades are a different style. Look at the point where the extension arm changes to the lift section. On the six bladed aircraft, the change is 90 degrees, (old design) and on the trial aircraft the change is 45 degrees, (a newer design).

Mark and cross,
You are both right, I missed that detail!

The 3 bladed flight was flown with cut down IRB's with SC 1095 airfoils and titanium spars. The original 53D has NACA 0012 airfoils and aluminum spar blades. Using the newer blades gave better data for the real purpose of the test, to determine the performance for the newer Sikorsky designs.

When the BV 234 was first introduced to the North Sea one of the assurances given to the Shell passengers was 'Twin Rotor Safety'. They honestly believed that it could fly on one rotor.

If I'm not mistaken, there is/was a one-bladed helicopter that flew. Bolkow 101 I think.

Monk

Like this? The Bo-103

http://www.luftrettung-hamburg.de/as...ges/BO_103.jpg

And the Bo-102 Helitrainer

http://www.geocities.com/capecanaver...o103vistas.gif


http://www.eurocopter.com/site/docs_...histbo102g.jpg

I bet its easy to track:} - and I bet you cant fly that with one missing:}:}

I dont really see the point of a single bladed design as wouldnt you still have the same rotating mass but less lift?

What are the benefits? :confused:

For the interested :8, or the very bored :bored:

Research and development work on a Single-Bladed All Electric Rotor

It appears that the single-bladed rotor will work well in hover and in vertical climb. Forward-flight is the problem. It's unfortunate because it would have been a simple and fun project to build.

Dave

I would hate to be the guy that lifed the hub bearings on the BO-103!!:eek:

Even though the mass balance is there, effectively it is as if the cyclic was going around the box at Nr. The vibration must have been awful. The mass could have been set lower than hub to generate an equal and opposing hub moment to the lift, but this would only work for 1g. Any actual cyclic input would still lead to out of balance moments, hence a means of 1P vibrational energy getting into the structure.

I wasn't sure if that hub was teetering - it's hard to tell from the hiller bar. However, cyclic vibration is why hingeless hubs always have 3 or more blades...

Mart,

Vibration should only have been a problem during any attempt at forward flight. It should not have been a problem during vertical; climb, hover and descent.
See the links at the bottom of this page http://www.unicopter.com/B465.html

Dave

Here is the Boelkow hub plus additional information on the craft. http://www.unicopter.com/B472.html

can you fly with one blade
 

A friend of mine was test starting the engine on a 22. The machine was minus its main blades, but had tail rotor blades. The engine fired and a split second later one tail rotor blade broke loose, the next second the tail rotor gearbox plus a section of the boom departed and was found later about eighty yards away. The belt drag on the pulleys was enough to spin the drive train up.:O:O:O:O

I wouldn't mind seeing the video of that!

In most cases it won't work very well....
 

We lost a S-61N in the North-Sea in 1978 due to a spindle brakedown followed by a blade loss. They found helicopterparts on the seabed covering about 1 sq.km. due to domolation. 21 souls lost.
Another S-61N (Brazilian) actually flew into the sea due to severe vibrations in June 1997. The pilots lost control completely. The wreck was picked up from 800 meters depth. There are 2 theories:

-One blade abration strip came loose. The weight is 340 grams, but due to angle of speed it induces much, much more. Heavy lateral imbalance!
-Another theory is that on blade broke and lost approx. 1/3. This was found on the seabed about 100 meters from the wreck. The rest of the blades were twisted around the hub as they met the water.
2 of 20 lost their life.

Conclusion: NO :=

I am a bit of a practical man if I do say so myself. And yes I did bear with you for the last couple of days. SO...experimentation aside, and/or removing a blade on the ground for test purposes is one thing, the fact of the matter if you lose a blade in flight you're screwed! Occupational Hazard.

BWB

PS

I found the research many of you did enjoyable to say the least. Burned alot of my time while weathered out in the bush. thx

After reading here how death is almost unavoidable when the MR becomes unbalanced, wouldn't it be a life safing option when it is possible to "just eject" the oposing blade?

That would probably give enough stability to safely autorotate ...