3 engines helicopter

[saloon64]

Hi everybody!
A friend of my told me that crews operating on EH101 or Ch53 shut-down everytime one engine during cruise. I'm a bit surprise by his propose. I found an article wich explained that a crew during a csar mission had shut down one engine due to the long distance, but it was exceptional.
If somebody who knows what is the reality it could be useful for my helicopter knowledge!
Thanks by advance

[airborne_artist]

News: EH-101 demonstates SAR & Rescue credentials (http://www.helis.com/news/2000/eh101sar.htm)

"A key feature of the EH101 in SAR service is its ability to undertake long range cruise on two engines whilst reverting to three engines for the rescue operation. The three-engine configuration is especially significant in search and rescue operations since, unlike current SAR helicopters, the EH101would be able to continue with its mission even if one of its engines failed in the hover."

Rotor & Wing Magazine :: Presidential Debate (http://www.aviationtoday.com/rw/military/vip/1466.html)

"Both the EH101 and S-92 were designed as Sea King replacements, albeit for different missions. In the late 1970s, AgustaWestland (http://www.aviationtoday.com/search/?query=AgustaWestland) (then EH Industries) aimed at a helicopter that would pack more fuel and sub-hunting electronics in the Sea King footprint aboard British and Italian warships. To carry about 50 percent more than a Sea King, yet recover from a hover in an engine-out emergency, the EH101 used three engines to turn its five-bladed main rotor."

[The Helpful Stacker]

I may be (probably am) wrong but isn't there an issue with power/weight ratio on the EHI-01 which means it can't make use of its designed ability to turn an engine off for more economical cruising other than in very specific circumstances?

[ShyTorque]

Perhaps EHI 01 crew will comment on the SOPs but it's a fact that two turbines at high power are more efficient than three at medium power so I see no real issue with it.

Thirty years ago, when this aircraft concept was being discussed between the UK's military (to decide on the Air Staff Target), I understood that the Royal Navy demanded an aircraft that could continue to hover if an engine failed. Due to the limitations and relatively low capability of the available engines in those days, some lateral thinking saw that on an aircraft of this size, three engines was actually more practical than two.

Delays to the aircraft occurred because of the inherent complications of a three engined helicopter main gearbox; I recall reading an article some years ago that claimed only one company in the world was capable of machining the casings.

[Matthew Parsons]

I may be (probably am) wrong but isn't there an issue with power/weight ratio on the EHI-01 which means it can't make use of its designed ability to turn an engine off for more economical cruising other than in very specific circumstances?

You can normally get a better range with the two engine cruise.

There are concerns with wanting the third engine should you require coming to a hover, and you have to be aware of height loss should you lose one of the two operating engines. Because of those considerations, it is only wise to consider two engine cruise when you're planning long distance cruises.

Matthew.

[Jack Carson]

The H-53E operators manual allows for dual engine cruise should mission requirements dictate. Specific fuel consumption improves by about 7% and adds about 50 NM to the aircraft’s maximum range. Twenty five years ago I was provided with the opportunity to fly the Wessex 5 off of HMS Hermes. The Wessex also allowed one of its two engines to be secured for long range cruise. One fond memory that sticks in my mind was what a great machine the Wessex was. Beast is the first word that comes to mind. :O

[CARLOS82]

Hello

We at Portuguese Air Force use TEO (two engines operations) for long range operations.
The only bad thing in TEO is working in cold weather because the first limitation is the TIT, and if you have to turn on the intakes and anti-ice system the TIT will rise and you have to reduce the power applied.
And you can safely fly away from a hover with 92% of torque applied if you have a engine failure.


FlySafe:ok:

[spinwing]

Mmmm ....

And in the mid 1960s early 1970s the French Super Frelon SA321 was doing all this then! ... so whats new ?

:}

[Jack Carson]

Spinwing makes a very valid point. The Super Frelon was a three holer back in the 60’s. The number of engines was more a function of the lack of any larger power plants available at the time that would permit a two engine design rather than an over powering desire to have sufficient OEI power. Typically one designs to a lift requirement not an OEI requirement. In the case of the H-53E, it was proposed as an Engineering Change Plan (ECP) to and existing design, the CH-53D. The requirement was for a 100% increase in payload (8 tons to 16 tons). This was accomplished with a 50% increase in power by installing a third engine. Only 16 were to be built. The program finally matured after more than 200 machines. A later requirement for an OEI fly away capability from a down wind TOW operation precipitated the installation of three 5000 ESHP T64-GE-419 engines in the USN’s MH-53Es. :8

[Fareastdriver]

The Super Frelon had three engines with a Sikorsky S64 rotor and tail rotor assembly to hold it up. This made it the only French designed helicopter with an anti-clockwise rotation viewing from the top. In the late seventies there was a line of them in Aerospat's hanger awaiting clearance from the White House before they, and their American components, could be shipped to the Peoples Republic of China..

[calaim]

The EH101 burns +/- 900KG/Hour with the 3 engines operative.
By shutting down engine #3 the fuel consumption goes down to 700kg, that's why we do TEO cruise ( Two engines operative) for long range.

[Camp Freddie]

and you have to be aware of height loss should you lose one of the two operating engines

what is the height loss if you go down to single engine in the cruise?
or i could say what is the "safe sector altitude" for going from 2 to 1 engines, till you get the 3rd going ?, I bet its got some fancy name !

CF

[Matthew Parsons]

Camp Freddie,

We don't know. I'll be testing to determine that later this year. However, if you can start the engines in less than one minute and can reduce your rate of descent in an autorotation to 1500-2000fpm, then its a safe bet that your altitude loss would be less than 2000' when you have one engine helping.