Floats on skid helicopters how effective they are.

[Rwy in Sight]

On February 11, 2016 an AB212 crashed on the island of Kinaros while on night time antiship warfare exercise with the loss all the crew.

Although I understand it is better to let the investigation run its course I got talking with a friend with an aerospace degree from the UK - so he does have knowledge. The question in popped up in the conversation was whether skidded helicopters equipped with floats roll upside down, when ditched. My friend said the crew would rather try to autorotate to a more distant place rather than ditch on floats.

So that prompt me the question provided you don't have problems with the weather large waves etc. can the floats keep a skided helicopter upright to allow the crew to evacuate easily - without using special underwater techniques?

Thanks for your answers.

[Heli]

Your friend may have a degree, but not the knowledge. How unusual.

If you're referring to permanent floats, they are designed for water operation and I can't see what is the query.

If you're referring to emergency pop-out floats, they are designed to keep the machine upright within certain limits, e.g. sea state, wind, etc. The ability to 'autorotate to a more distant place' also indicates a gross lack of understanding of helicopter operations: if you're in autorotation your choice of landing area is between what you can see through the chin bubble, and what is behind you. The concept of changing your mind for a landing some miles away is fanciful.

[Rwy in Sight]

Your friend may have a degree, but not the knowledge. How unusual.

If you're referring to permanent floats, they are designed for water operation and I can't see what is the query.

If you're referring to emergency pop-out floats, they are designed to keep the machine upright within certain limits, e.g. sea state, wind, etc. The ability to 'autorotate to a more distant place' also indicates a gross lack of understanding of helicopter operations: if you're in autorotation your choice of landing area is between what you can see through the chin bubble, and what is behind you. The concept of changing your mind for a landing some miles away is fanciful.

Thanks Heli,

I was referring mainly to emergency floats as the helicopter involved was an AB-212 and it is equipped with emergency floats with skids for normal operations. So I take those floats can keep the craft upright as long as they operate within their limits.

To rephrase my initial comments, the question is whether an AB-212 pilot will try to autorotate to crash landing rather than ditch because of concerns of the helicopter rolling over after the ditch.

Looking forward for more comments.

[Heli]

The 212 is a twin engined helicopter: autorotation occurs when all power is lost, be it one engine or multi engine doing the driving.

If there is a premeditated ditching due to other failures (tail rotor, MR control, loss/lack of fuel) then there are techniques for such a landing, effectiveness of which depend on swell, wave height, wind, etc. Such a premeditated ditching would include inflating the emergency floats prior to entering the water.

An autorotation is a power off approach and choice is reduced in a number of factors, not least of which would be the opportunity to choose the actual touch down point. Autos are energy management and at the bottom the trick is to throw two (airspeed and Rotor RPM) of the three (height, airspeed and RRPM) away to effect a zero speed cushioned touchdown, hopefully into wind. This may not meet the ideal into wave/swell choice. Again, popping the floats would be done when within inflation parameters, prior to touchdown, and they should provide stable buoyancy for the 212 once on the water.

Emphasis on "should".

[Rwy in Sight]

Thanks again for the clear explanation (of both autorotation and floats). I wish you to only have a theoretical knowledge of the floats and autorotation and never need to practice for real what you wrote.

Take care.

[Avtrician]

The object of auto rotation is to have a controlled descent to a safe landing, not a crash landing. Crashes should be avoided where possible. If the chopper has floats fitted, or emergency floats, then if water conditions are ok, then a trained pilot should be able to auto rotate to a safe water landing.

I have been in an RAAF Huey many times when practising auto rotations, and not once did we crash. The run on from arriving on the ground with forward speed could be a bit rough, but definitely not a crash.

[Rwy in Sight]

Thanks Avtrician. The investigation is conducted under Armed Forces procedures so the only thing announced so far is that about a high speed crash. However I have a question: is autorotation possible is there is a damaged gear-box?

[Heli]

If you have a damaged gearbox then you can be in a world of strife, depending on which gearbox and what damage. The 212 has a main gearbox (MGB), tail rotor gearbox (90° box), combining gearbox and the 45° box! Either the 45° or 90° boxes will bugger up your tail rotor drive and are a PITA depending on airspeed and power settings. Combining box takes the power from the two P&Ws into a single output shaft which drives into the MGB, failure of which can be attention getting.

A MGB failure/damage will predominantly require power to continue to rotate the blades in order to control and continue flight. Entering auto removes that power and can exacerbate the situation, so a controlled minimum power approach to an emergency landing is the best option.

[500N]

For those pilots who have replied (or not replied !), how many of you have:-

1. Auto rotated to land the aircraft in an emergency ?
2. Ditched in water ?

[Heli]

1. yes
2. float and floating hull endorsements, but not in anger