How do heli floats work?

[G-ANDY]

I see heli's all the time outside my office window, and I see their floats packed like a life jacket on the skids. But how do they work?

1). I guess they are deplayed like a life jacket when the outside pressure (say the pressure when immursed in 1m of water) gets to a certain amount and they inflate?
2). How big do they get when fully inflated? I guess they must be fairly big to support the heli - but then do they block the doors stopping the crew/pax from escaping?
3). Do they allow the helicopter to float above the water, or sitting slightly below? It seems as though it might be top heavy with the engine placed so high, causing the heli to flip over in the water, but floating upside down?
4). In the in the whole scheme of things, how good usefull are floats?
5). Does anyone have any photos or video clips of any in action?

Many thanks,

G-ANDY

[BlueEagle]

Going back over 35 years now to the JetRanger, they were inflated by the pilot who had a switch on the cyclic column connected to a gas bottle in the baggage compartment.

I think you would get a complete set of answers if you posted this in the RotorHeads forum.

[S92mech]

The floats must be manually deployed on most types of helicopters but some have water activated automatic deployment. There are high pressure gas bottles that inflate the floats, some aircraft types only have one bottle but some types can have several filled with helium or nitrogen. I have videos of S-92 floats being tested, but the file is very large. PM me and I'll send you some pictures of a 206 with floats inflated.

[SASless]

Usually....about halfway...half the time or completely as advertised when setting on the ramp doing a float circuit check with the BossFellah watching.

[Aesir]

Here is a Bell 212 with floats inflated for testing purposes:



The 212 has 4 automatic switches of wich at least 2 have to be submerged in water to release the floats if the pilot has the float system armed.

There is also a manual float release.

[helicopter-redeye]

On the 44 Clipper, take the pin out of the bottle value before flight (not during the emergency....)

Remove the safety catch from the collective trigger (slide and lock when coasting out/ relock when coasting in).

In the unlikely event of an emergency over water, apply pressure to trigger when required, observing the revised Vne and other speeds (incl autorotation) that now apply.

Gas leave bottle under F LH seat and inflates within 2 seconds.

Same size as full utility floats, and just as buoyant

[chopperdr]

have a boatload of pictures of float installs. have been involved in many protoype and stc flight test / installs on floats. pm if you want me to send some jpegs.
also note:
utility floats, emergency and ditching floats are all different sized and have their own unique abilities, make no mistake, you cannot takeoff after a water landing with ditching floats, as the tailboom will most likely be underwater
dr

[Non-PC Plod]

Various different ways of inflating them (auto or manual) - you will find that the principal use of floats is to make the dead aircraft easier to recover. You are dead right that the aircraft are top-heavy, and will almost always turn turtle unless the sea is a flat calm. That is why anyone in their right mind who flies over the sea does a helicopter underwater escape course!

[JimL]

Non-PC Plod,

The principal reason for using floats is to ensure that the helicopter remains in an upright position during the period in which an evacuation takes place.

Helicopters which have been certificated for ditching have a specified sea state for which entry procedures and stability have been established (usually modelled). The advisory material indicates that this sea state should be the 'reasonably probable' conditions over which the helicopter is flown - it is indicated in the text that this might be sea state 4.

Helicopters which are not certificated for ditching can also be equipped with flotation equipment but entry procedures and sea state are not established by the manufacturer (it is likely that the floats used on these helicopters are the same).

More modern helicopters have obtained ditching approval for sea states up to 6; analysis indicates that the North Sea has a sea state higher than 4 for 30% of the time in winter.

Because it is reasonably probably that the helicopter will invert following a ditching in high sea states, all helicopters operating for oil support in the North Sea have a 'pop-out-window' at each seat row. These windows help to ensure that all passengers and crew members can evacuate within 'breath hold' time following an inversion.

The UK CAA are about to publish a paper which fully discusses the issue of ditching; it will contain a number of previously published and unpublished papers on the subject.

Recovery of the helicopter is an economic issue and has nothing to do with the provision of flotation equipment.

Jim

[Thomas coupling]

Jim, your navy memories are fading!
Having been a 'waterbird' instructor for my sins during my Canadian exchange, I can guarantee that anything over state 2 (ish) is going to cause severe stability problems to big helos, even those designed to ditch (S61 etc).
Smaller ones would not fare as well, I would suggest. It is true, flot bags are only there for one reason, to present the crew with adequate assistance to get out immediately after ditching.
The flot bags do NOT cater for:
Swell - blades striking wave crests.
Ingress of water into the mainframe - doubling the weight of the helo and thus exacerbating the orientation of the cabin.

The biggest problem for (most) helos is their tendency to tip over due to their weight distribution. This might be in the shape of a roll left or right, or a nose dive!

Either way, UNLESS you are sitting on a mill pond, I wouldnt saty in side the cabin for longer than necessary.

Dunker training is a MUST if you are a frequent 'feet-wet' flyer.

[Lu Zuckerman]

Pop-Out-Float trivia

The Pop-Out-Floats were developed by the USCG Rotary wing development unit at Elizabeth City, North Carolina. They were installed on a HO3S-1G.

See attached photos: http://www.uscg.mil/hq/g-cp/history/...rsky_HO3S.html

[Heliport]

Pics posted on other threads --

[Mars]

An interesting summary of the requirements (and deficiencies in the requirements) for overwater flight:

Overwater helicopter operations are permitted in the knowledge that emergency situations may arise which require an immediate and forced landing. Accordingly, ICAO Annex 6 Part 3 paragraphs 2.2.11 and 4.5.1, and national operating rules specify those circumstances where approved flotation and safety equipment must be carried, and ICAO states that Sea State shall be an integral part of ditching information.

Currently, in both JAR and FAR rotorcraft airworthiness requirements, there are two standards of flotation equipment which can be approved. The first, which is applicable to both JAR/FAR 27 and 29 is Ditching Equipment. The second, which is only applicable to JAR/FAR 27 is referred to as Emergency Flotation Equipment. The airworthiness requirements applicable to both are generally the same except that Emergency Flotation Equipment is not required to meet any prescribed standards for the water entry phase.

FAA Advisory Circulars AC 27-1 and 29-2 define Ditching as an emergency landing on the water, deliberately executed, with the intent of abandoning the rotorcraft as soon as practical. For the purposes of this paper, it is assumed that Emergency Flotation Equipment is intended to achieve the same aim as Ditching Equipment.

Following a ditching onto the surface of the water however, there are conditions which will cause a helicopter floating upright to capsize before abandonment has been completed. In these circumstances, evacuation will have to be carried out from an inverted and flooded cabin with the occupants probably suffering from severe disorientation and cold water shock. Service experience has brought about a number of design features which can significantly enhance occupant survivability in these circumstances. A number of these features are currently not required by the airworthiness codes.

Accident data indicates that unintentional water impact is also to be expected and, in otherwise survivable crashes, the major cause of fatalities is drowning. There are currently no crashworthiness certification requirements specific to water impact. Recent research into accident data has concluded that improvements in the crashworthiness of flotation equipment would significantly enhance post crash survivability.

[G-ANDY]

Thanks everyone!

Thanks for all your answers - I now get the general gist of the inflatable floats.

Great photos too Aesir and Heliport. Its obvious now that the floats do block the doors, but then you probably wouldn't be able to open the doors with the water pressure outside - hense the windows which pushout.

Lu - I like the last photo on that site you posted of the two people sitting on the top of the heli. I wonder if they were able to start it back up and fly home!!?

I'm quite impressed by the photo of G-TIGK - it's floating pretty high up in the water in rough seas and thats a big heavy heli too!

Thanks again,

G-ANDY

[Heli-Ice]

Nice to have you back Lu.

[Mars]

G-ANDY:

Don’t feel obliged to sum up the discussion because you instituted the thread - your assumption about the doors and windows is incorrect. (It is also not clear that the thread has exhausted itself yet.)

Each aircraft type for which an application for certification for ditching is requested has to show compliance with the requirement for emergency exits; the number and type of these exits is governed by the passenger capacity and all required emergency exits must be above the water line. Specifically, FAR/JAR 807(d)(3) states that Flotation devices, whether stowed or deployed, may not interfere with or obstruct the exits.

The presence of ‘pop-out-windows’ is an additional safety element - they are not the emergency exits that are required by certification; rather they are related to JimL’s remark:

Because it is reasonably probably that the helicopter will invert following a ditching in high sea states, all helicopters operating for oil support in the North Sea have a 'pop-out-window' at each seat row. These windows help to ensure that all passengers and crew members can evacuate within 'breath hold' time following an inversion.

The breath hold time following cold-shock (even when wearing survival suits) is in single figures.

Emergency exits and doors can cause additional problems; when G-TIGK’s door (see the picture above) was released using the emergency handle, it floated upwards and snagged; the consequence was a jagged edge which punctured one of the liferafts.

Additionally, JimL was not quite correct when he referenced the sea state:

…analysis indicates that the North Sea has a sea state higher than 4 for 30% of the time in winter.

in fact:

A recent study of wave climates along a representative selection of main helicopter routes in the northern North Sea and West of Shetland (regarded in JAR-OPS 3 as a Hostile environment), indicates that Sea State 4 will be exceeded on 26-36% of occasions over the whole year. During the winter period between December-February, this increases to between 51-65%. If the certification requirement was raised to Sea State 6, the risk of exceedance would fall to a maximum of approximately 3% over the whole year and 3-7% in the winter months.

Hence the attempt by the manufacturers to improve on sea state 4 for ditching approval; for example the S92 moves from sea state 4 to 6 by adding two additional bags one on each side of the fuselage at the back of the cabin.

TC is also correct in that the modelling of stability is done with tanks generating a regular wave form - it is the breaking of the wave that causes capsize not necessarily its size.

[Arkroyal]

Not very well, in most cases