Mi-24 Hind + hovering = impossible?

[General Mcclintock 0]

I have recently heard that the Mi-24 Hind cannot Hover.

Is this true?

The reason for this was said to be the wings generating downforce due to the rotor wash.

But I cannot make all the calculations fit in this case.

If it is true, is it fixed on later models? Like the Mi-35?

[Commander-598 0]

If it couldn't hover, how could it ever get off the ground(litterally) and go into production?

[Messiah 2]

hovering, and getting off the ground are two completey seperate things... from what i've read, aquiring the skill and ability to execute a stable hover, is the hardest skill to master when flying rotary wing.

although it does seem strange that it would be unable to hover - but intriging... i may have a search and see what i find

[finarvas 1]

Quote[/b] ]Its high loaded weight can also limit its effectiveness as a helicopter, some reports state that with a full load the Hind needs a rolling take-off and also cannot hover. The problems with the dual-role Hind have prompted the development of the Mil Mi-28 and also the Kamov Ka-50 to replace it in the gunship role.

Also, the wings interfere with the aircraft's ablity to hover and take off vertically. In fact, the Hind is certified to hover for only about 200 hours during its entire lifetime, a consequence of its emphasis on forward speed.

http://en.wikipedia.org/wiki/Mi-24_Hind

[Messiah 2]

was about to post the same... the following is also rather alarming:

Quote[/b] ]The comparatively high size and weight of the Hind limit its endurance and maneuverability. In tight banking turns it can roll alarmingly as the wings lose lift - this was noted during test-flights in 1969 but has still not been entirely eliminated. To counter this vulnerability the Russians operate the aircraft in pairs or larger groups, with attacks carefully coordinated to strike from multiple directions simultaneously. Another weakness was the possibility of the main rotor striking the tail-boom during violent maneuvers

like many things with Russian design, it seems they sacrificed manouverability and efficiency, for raw power (both speed and weapons)

one Afghan rebel is quoted as saying during the afghan war with Russia:

Quote[/b] ]"We do not fear the Soviets. We fear their helicopters."

some other interesting facts:

Quote[/b] ]The cockpit was heavily armoured and could withstand even .50 cal rounds, but the Hinds tail is extremely vulnerable due to the lack of armour in that section.

The heat-seeking nature of the anti-aircraft weapons employed by the Mujahideen combined with the Hinds exhaust being directly under the main rotor caused the aircraft to disintegrate if hit. This was remedied later by countermeasure flares and a missile warning system being installed into all Soviet Mi-4, Mi-8, and Mi-24 helicopters giving the pilot a chance to evade the missile or crash-land.

[hellfish6 7]

I've seen a film clip of a Hind hovering to engage a target with AT3 missiles. If the Hind rarely hovers, I'm curious to know why the Soviets would equip them with ATGMs. As I understand, wire guided ATGMs like the AT3 need to have stable firing platform.

[llauma 0]

Most helo's have problems hovering on a spot. It might hover just fine for a while until the conditions of the turbulence get's perfect (or should we say bad) and the helo loses all lift. I think it's called a vortex ring. The vortex ring is one of the reasons why the Osprey keeps crashing.

So a helo as heavily armoured and heavy as the Hind will need lots of power to hover and the more power it has the more turbulence you'll get.

[shadow 6]

The vortex ring is usually not a problem for most helicopters. Its just that there are these bad apples (the Hind beeing one of them). Most gunships can hover pretty much as long as they need to inside the ground effect.

The vortex ring happens if the helicopter is descending very fast without any significant forward speed. What happens is that the rotors are beeing caught up in its own downwash. Basicly there is no longer any air to compress to generate lift. To get out of the vortex ring you need to gain forward speed or settle with power and hope the rotors will be able to generate lift again.

Only large rotors that compress alot of air can create a vortex ring while hover (not changing altitude). Like Llauma says; the Osprey is a good example. Chinooks are another good example. But for "small" rotors like on Cobras, Apaches, Blackhawks and Havocs etc the vortex ring is of no concern when hovering.

Also, 5 rotor blades instead of 4 have a greater potential to create a vortex ring (more air being compressed).

So 5 blades may generate more lift but its not without its side-effects.

Quote[/b] ]Also, the wings interfere with the aircraft's ablity to hover and take off vertically. In fact, the Hind is certified to hover for only about 200 hours during its entire lifetime, a consequence of its emphasis on forward speed.

I'm guessing the downwash stresses the ridiculously wide wings on the airframe (and thus blocking alot of lift and bouncing the air back up).

[Jinef 2]

The hind with standard loads can hover, turn and do the most normal things of helicopters.

However when you give it a full fuel load, troops and stick half a ton of weapons on it requires a rolling takeoff to get airborne and indeed cannot sustain hover without over-straining the engines.

Once the fuel is used it can hover again.

[Necromancer- 0]

Once the fuel is used it can hover again.

Untill you run out of fuel...

[gandalf the white 0]

Wow guys! that made for some interesting reading! thanks .

[Cpt. FrostBite 0]

The hind with standard loads can hover, turn and do the most normal things of helicopters.

However when you give it a full fuel load, troops and stick half a ton of weapons on it requires a rolling takeoff to get airborne and indeed cannot sustain hover without over-straining the engines.

Once the fuel is used it can hover again.

Early model huey gunships in Vietnam were so packed with ammo and weapons that they made a 'bounching' take off making small jumps before they actually got of the ground for real. Later the engines were improved and more powerfull (and bigger) huey models shipped to vietnam.

[SpongeBob 0]

The hind with standard loads can hover, turn and do the most normal things of helicopters.

However when you give it a full fuel load, troops and stick half a ton of weapons on it requires a rolling takeoff to get airborne and indeed cannot sustain hover without over-straining the engines.

Once the fuel is used it can hover again.

Early model huey gunships in Vietnam were so packed with ammo and weapons that they made a 'bounching' take off making small jumps before they actually got of the ground for real. Later the engines were improved and more powerfull (and bigger) huey models shipped to vietnam.

In other cases, the crew chief and gunner would run along side of the huey as it flew down the runway and as soon as the chopper cleared a couple feet off the ground, the crew would jump into the chopper.

[Warden 0]

Find the Book Chickenhawk, its by a Huey Pilot in Vietnam, goes into a lot of detail on those running starts, much harder when being shot at and surrounded by trees apparently!

[JdB 151]

Tactics for these kinds of helicopters is also different. NATO attack helicopters use hovering and concealment before firing off a sh*tload of ammo. Sovjet (and Russian?) tactics where (/are?) based on high speed passes over the target, to get in, fire at the target and be gone before the defenders could use serious firepower against the Hind.

Also, isn't the term ''gunship'' for armed transport helicopters like the Blackhawk or Huey and not for dedicated attack helicopters like the Hind, Cobra, Apache, Tiger etc?

[DaSquade 0]

Quote[/b] ]Most helo's have problems hovering on a spot. It might hover just fine for a while until the conditions of the turbulence get's perfect (or should we say bad) and the helo loses all lift. I think it's called a vortex ring. The vortex ring is one of the reasons why the Osprey keeps crashing.

So a helo as heavily armoured and heavy as the Hind will need lots of power to hover and the more power it has the more turbulence you'll get.

Reminds me of a video i saw some time ago (don't ask me what/where/..ext, as it was some time ago and i think it was from some kind of 'putfile' site). Shame i don't have it anymore and it is almost impossible i guess to find it again. Anyway, it was a movie of (afair) a blackhawk (could have been something large...as i said..don't really remember)...but it was at an airshow. The heli was hoovering (pretty stable) at about 20-30m for 1 minute or so, when it suddely DROPPED out of the air. All crewmen survived.

"What goes up, CAN come down!"

[shadow 6]

I believe that was a Sea King or Sea Stallion.

I remember seeing the video of the helo hovering, then suddenly it went down and flipped over on the side and you could see the rotor blades go all the way down through the ground (grass and dirt) several times before they started breaking.

[DaSquade 0]

Yeah, it could have been a Sea king or Sea Stallion (last i'm almost sure of it wasn't).

OFFTOPIC: (as it isn't a heli), but i think this is a bit simular:

harrier crash

[shadow 6]

Ran out of water maybe.

Or it could look like the pilot screwed up when he switched to forward-motion. The aircraft starts moving forward, but descends fast, then forward motion stops and the aircraft descends a little slower.

Quote[/b] ]Yeah, it could have been a Sea king or Sea Stallion (last i'm almost sure of it wasn't).

I think it was the Sea King. If I remember correctly there was absolutely no wind too (perfect if you want to create a vortex ring and not get out of it).

[Commando84 0]

cool reading, didn't knew that. i just thought it was start and go for choppers i only thought those ww1 , ww2 stuff that was unstable in the movies

[Edge 2]

Mi-24 Hind can hover, it's a helo. However, its ability to hover might be influenced by weapons loadout, cargo, amount of fuel, gravity center etc. Particularly Mi-24 has problems while hovering; for it may become quite unstable. However, on instrument panel of Mi-24, there is kinda "mode switch" for engines with one position for hovering.

In time of Iron Curtain, Czech Hinds (Mi-24V) patrolled mountains on border with West Germany. Czech Hinds and US Cobras often played kinda "imitate-me" game, which has nothing to do with politics or warfare but was pure demonstration of both sides' egos. There was an accident when Hind crashed because it failed during manoeuvre previously performed by Cobra, which involved low-forward-velocity flight and/or hovering.

After this accident, pilots were forbidden to run slower than 100 km/h to avoid further losses because the tricky combination of mountain weather and Hind's instability in hover.

Hind pilots of Czech Air Force prefer the running start just because it's much safer. Hinds normally taxi to the runway and follow similar procedures as normal aircraft, except of they run just about 50 meters before taking off the ground (I saw it, this running lenght is my mere approximation).

[Messiah 2]

same could be said with the Harrier Jump jet - it has the ability to hover, take off verticaly and land vertically, but in a military operation and use, its more typical and sensible to take off normally - there would be very few, if not no military applications for a Harrier to hover on the battlefield and shoot things... its not a Arnie film after all

There must be good reason for the prevention of hovering in normal usage though? From what wikipedia says, its a case of the chopper being too big and armoured/loaded etc to effectivly and safely maintain a hover, although it doesnt state it cant acheive it.

[Guest RKSL-Rock]

There must be good reason for the prevention of hovering in normal usage though? From what wikipedia says, its a case of the chopper being too big and armoured/loaded etc to effectivly and safely maintain a hover, although it doesnt state it cant acheive it.

There is - engine wear from heat damage.  Just like the Harrier hovering puts a lot of stress on the engines and rotor hub.  Add together al the unusual features of the Hind (wing config & large weapons load + cargo etc) and hovering it will be difficult but is possible as already stated, but it will also be at the expense of engine life.

If it overheats the radiators and cooling wont be able to cope and the engine will be damaged.  At the very least overheating cause loss of efficiency which means the engine can’t produce the power it needs to maintain altitude in a hover as easily.  Most aero engines are designed to operate with air moving over them to cool them - even jets - most helicopter engines have extensive cooling systems but even they have limits.  On the Harrier its 2 mins (as long a the water tank lasts) on the Hind with a full load i can’t imagine it would be too long.

[Scrub 0]

Speaking of heat, isn't the Hind's main rotor transmission prone to failure/fire due to the stress of long term hovering, and a poor lubrication system?  Seems I've read that more than once in the past 20 years.