What is that Cannister behind the APU ?

[Avio]

Been flying in the Hip very much and loving it. Noticed in the DCS modelling of the Hip, there is this huge vertical cylindrical cannister just behind the APU compartment. What is this and what is it for? This item does not seem to appear in most other Mi-8 in the real world.

 

[AlphaOneSix]

IR Jammer. Not modelled in DCS.

[Avio]

Thanks much AlphaOneSix ! Just curious, how does that work in the real Mi-8? For flares, it is a matter of fooling the IR missiles away from the Hip. But with the fixed cannister jammer on the Hip, how does it work to fool those IR missiles?

 

 

[Avio]

One more question here ... really trying to get to know this helo better.

What are those hole in the attached picture?

[Quadg]

1 hour ago, Avio said:

Thanks much AlphaOneSix ! Just curious, how does that work in the real Mi-8? For flares, it is a matter of fooling the IR missiles away from the Hip. But with the fixed cannister jammer on the Hip, how does it work to fool those IR missiles?

 

 

It only worked with 1st generation IR missiles with poor seeker heads.

basically its an IR lamp that blinds the seeker head rather than spoofing it away like flares.

like shining a torch in someone's eyes to blind them at night. all the seeker head sees is afterimages and it cannot track.

more modern missile seeker heads are not blinded or recover quicker. so the lamps no longer work. they actually make you an easier target. As IR homes on IR sources.

why the lamps have been removed or left on and disconnected in all russian aircraft. (its disconnected in our MI-8)

 

 

 

[Kang]

Wait, blind it? I thought ye olde IR missile jammer worked by 'blinking' (or pulsing rather?) and such suggesting to a missile that it was off target while it in fact was not, thus prompting it to 'correct' away.

[Northstar98]

On 10/18/2021 at 4:43 AM, Avio said:

Thanks much AlphaOneSix ! Just curious, how does that work in the real Mi-8? For flares, it is a matter of fooling the IR missiles away from the Hip. But with the fixed cannister jammer on the Hip, how does it work to fool those IR missiles?

The jammer is known as the L-166 "Espanka" AFAIK.

As for how it works, the best resource I can give you is 'History of the Electro-Optical Guided Missiles.pdf' which can be found here.

To summarise, early missiles used a tracking technique known as 'spin-scan' (described on pages 8-9), this uses a spinning reticle with sectors that are opque, and sectors that are transparent.

If the target is off-centre, it'll show up in one of the transparent sectors as the reticle spins, this generates an AM signal, and the phase of the modulation envelope of said signal encodes position information of the target (the carrier frequency of which is the frequency of the reticle, which is determined by how fast it spins).

How the jammer works (described on pages 30-32) is that it pulses strong IR light, with a frequency equal to that of the spinning reticle (which relies on intelligence of the threat missile), but out of phase with the signal from the target, this causes the missile to make erroneous corrections, driving it away from the target.

Another great source of information (and the source the above .pdf uses) is Aircraft Infrared Principles, Signatures, Threats and Countermeasures (NAWCWD TP 8773) which can be found here, with pages 69-72 describing 'spin-scan' seekers and pages 93-98 describing thermal jammers.

 

Note, page numbers are the actual page numbers on the document, not the page numbers the pdf reader uses.

Edited December 27, 2021 by Northstar98
spelling

[AlphaOneSix]

14 hours ago, Avio said:

One more question here ... really trying to get to know this helo better.

What are those hole in the attached picture?

The ones on top are just openings to let air into the engine compartment to help with cooling. On the side, those are the openings for the tubes from the engine compressor bleed valves. Below a certain N1 RPM (84-87%), the compressor bleed valves open to let air out of the compressor to prevent compressor stalls.

[Avio]

Thank you all good folks for the very, very helpful pointers. Learning so much from just this forum over the years !

Continuing to find the DCS Mi-8 to be so awesomely well modelled masterpiece, a class well above many others. Years of flying in this DCS piece seem to reflect the way the real Hip moves as shown via so many youtube clips.

The only bugging modelling I have question on, would be that of the retreating blade stall behavior. Saw on youtube, as well as tried it myself, and the Hip always first rolled to the left, followed by strong, almost vertical pitch-up. Tried to follow some online discussion, but no firm conclusion. In theory, a blade stall on the right, should be followed by a right roll, not left (the DCS Mi-24 does that). Some discussions talked about gyro precession, thus the huge pitch-up. But why the "right" roll at the start of the event? Does the entire sequence (right roll, then pitch-up) modelled reflect the actual behavior of that of the real Hip?

Hope to get some illumination on this. Thanks!

 

[Avio]

Sorry to have some many questions .....

In the attached picture, what are those items marked out :-

1) The hole besides the APU exhaust

2) The loop of string that goes to the horizontal fin

3) That piece of hump behind the engine exhaust

4) That device near the weapon rack -- is that the gun camera?

5) The piece jutting out from the rotor blade that looks like a trim tab

Thanks in advance !

 

[AlphaOneSix]

1 hour ago, Avio said:

Sorry to have some many questions .....

In the attached picture, what are those items marked out :-

1) The hole besides the APU exhaust

2) The loop of string that goes to the horizontal fin

3) That piece of hump behind the engine exhaust

4) That device near the weapon rack -- is that the gun camera?

5) The piece jutting out from the rotor blade that looks like a trim tab

1) That's the air bleed for the APU compressor. When not used to start the engines, the APU dumps a lot of air pressure overboard. During engine start, a diverter valve prevents air from being dumped overboard and is directed forward to the engine air turbine starters.

2) Antenna for Yadro-1A radio set.

3) Modification to Mi-8s that have a second AC generator installed. Mi-8s prior to the Mi-8MT only had a single AC generator. Starting with the Mi-8MT, a second AC generator was added that sticks out from the left side of the main gearbox and requires that blister in the panel in order to fit.

4) Gun camera, yes.

5) Trim tabs, yes.

[Sobakopes]

18.10.2021 в 21:51, AlphaOneSix сказал:

The ones on top are just openings to let air into the engine compartment to help with cooling. On the side, those are the openings for the tubes from the engine compressor bleed valves. Below a certain N1 RPM (84-87%), the compressor bleed valves open to let air out of the compressor to prevent compressor stalls.

Can you name pros and cons of mi8 helicopters? You seem to be knowledgeable. 

[AlphaOneSix]

Pros and cons are pretty hard, because a pro can be a con and vice versa, depending on the situation. In general...the aircraft is very reliable. But since it is such an old design, it is not as easy to maintain as more modern aircraft. However, since it is so reliable, maintenance mainly consists of adding grease and doing regular inspections. We like to refer to it as the AK-47 of helicopters. It is not as sexy, fast, or maneuverable as more modern aircraft, but it is dependable and relatively cheap. There are so many in service all over the world that parts are not terribly hard to find. Upgrade after upgrade keeps it relevant compared to more modern helicopters, but it's an old design and that hurts it a little, in my opinion.

[Sobakopes]

43 минуты назад, AlphaOneSix сказал:

Pros and cons are pretty hard, because a pro can be a con and vice versa, depending on the situation. In general...the aircraft is very reliable. But since it is such an old design, it is not as easy to maintain as more modern aircraft. However, since it is so reliable, maintenance mainly consists of adding grease and doing regular inspections. We like to refer to it as the AK-47 of helicopters. It is not as sexy, fast, or maneuverable as more modern aircraft, but it is dependable and relatively cheap. There are so many in service all over the world that parts are not terribly hard to find. Upgrade after upgrade keeps it relevant compared to more modern helicopters, but it's an old design and that hurts it a little, in my opinion

Do you think it's fair to compare mi8 and black Hawk? 

[AlphaOneSix]

Comparisons between the two are inevitable. However I believe it is unfair to compare them. Very different design philosophies. 

[Avio]

Thanks so much once again, AlphaOneSix !

About the Mi-8 reliability, typically what are the service life span of its major parts, such as rotor blades, etc.? Are there those that push close of its life span and still fly reliably?

By the way, overlooked one more part to ask about -- that pointed "horn" thing that sticks out from below the nose and the bottom end part of the tail, as marked on the attached pic. What are these? They don't seem to serve anything. This guy seems to be endowed and attached with a gazillion of parts all over !

About the Trim Tab, they are not adjustable, and not trimmed like in aircraft wings right? Not sure how they work out as trim.

Thanks!

Edited November 1, 2021 by Avio

[AlphaOneSix]

6 hours ago, Avio said:

Thanks so much once again, AlphaOneSix !

About the Mi-8 reliability, typically what are the service life span of its major parts, such as rotor blades, etc.? Are there those that push close of its life span and still fly reliably?

By the way, overlooked one more part to ask about -- that pointed "horn" thing that sticks out from below the nose and the bottom end part of the tail, as marked on the attached pic. What are these? They don't seem to serve anything. This guy seems to be endowed and attached with a gazillion of parts all over !

About the Trim Tab, they are not adjustable, and not trimmed like in aircraft wings right? Not sure how they work out as trim.

Typical time before overhaul for major components can vary quite a bit, but is typically 1,500 to 2,500 hours between overhauls, with total lifetime of 8,000 to 20,000 hours. This is quite a bit less than comparable Western aircraft, but the entire overhaul philosophy is very different. Western aircraft parts typically go 5,000 to 20,000 hours before overhaul, and don't have a lifetime limit at all. It seems to me that it is generally assumed that many operators will lack extensive training and facilities to do heavy maintenance themselves, and so the overhaul facilities fill that role, while Western manufacturers push a lot of that extensive maintenance down to a lower level. This is part of what makes Western aircraft so much more expensive, not just the aircraft themselves, but the parts, tools, facilities, and training. Russian helicopters are easier to maintain in the field and in harsh environments and with less well-trained maintainers, but have to go back to an overhaul facility more often.

I'm not sure what thing on the nose you're referring to, but the thing on the tail you circled is the IFF antenna.

The trim tabs are adjustable, but not in flight. They are adjusted as part of a maintenance procedure to make the rotor smoother in flight, which we call tracking and balancing. We use weights, trim tab, and pitch control link adjustments to reduce vibrations from the main and tail rotors (tail rotor only uses weights for balance, no trim tabs or pitch change link adjustments).

[Avio]

Thanks again very much for the helpful elaborate insight. The overhaul time periods you quoted seem to range quite widely. I guess it depends on how heavily (or roughly) used each specific Hip is in the field.

Flying the Hip in DCS feels totally safe as far as component reliability is concerned. In the real world, which critical component needs the most attention to? Which tends to fail more often? Setting failure mode on in DCS just doesn't feel realistic, as a 1 in 100 chance of failure is way too high. If only DCS allows for a failure rate mirroring that of the real Hip in the field, that would be nice. Better still, a maintenance mode like that in A2A aircrafts in MSFS.

That part about the trim tabs was really good. Nice to know how helo's vibration is tuned out.

The part under the nose is as shown in the attached (triangle piece behind the pitot tube). It looks like the one at the tail, so I assume it is another IFF antenna? The Hip needs two IFF?

[AlphaOneSix]

11 hours ago, Avio said:

Thanks again very much for the helpful elaborate insight. The overhaul time periods you quoted seem to range quite widely. I guess it depends on how heavily (or roughly) used each specific Hip is in the field.

Flying the Hip in DCS feels totally safe as far as component reliability is concerned. In the real world, which critical component needs the most attention to? Which tends to fail more often? Setting failure mode on in DCS just doesn't feel realistic, as a 1 in 100 chance of failure is way too high. If only DCS allows for a failure rate mirroring that of the real Hip in the field, that would be nice. Better still, a maintenance mode like that in A2A aircrafts in MSFS.

That part about the trim tabs was really good. Nice to know how helo's vibration is tuned out.

The part under the nose is as shown in the attached (triangle piece behind the pitot tube). It looks like the one at the tail, so I assume it is another IFF antenna? The Hip needs two IFF?

The overhaul time periods have nothing to do with how the aircraft is operated. They differ based on the part itself and who/how the overhaul is performed.

The components we pay most attention to are the ones that will kill us if they fail in flight. Tail rotor, tail rotor drive shaft, main rotor blades, main rotor hub, swashplate, that sort of thing. Nothing fails very often. I've been involved with a fleet of 10 Mi-17s for 15 years, and we've had two engine failures (both shortly after an overhaul) and one tail rotor drive shaft failure (caused by water getting into an oiled coupling). We also had a tail rotor gearbox fail in such a way that pedal inputs were no longer possible, which was caused by the failure to properly modify the gearbox at overhaul with updated internal parts. Other things have been caught during inspections that could have been a big problem had they failed in flight, but these things are quite rare. Usually things go bad slowly and are caught during scheduled inspections and replaced. Or the things that break don't result in the aircraft crashing, they're just a nuisance and are fixed as time and parts permit.

I've never seen an IFF antenna under the nose, only on the bottom of the tail. I suppose there could be two antennas, or I could be wrong and that's actually an antenna for something else. The one on the tail has always been the IFF antenna in my experience.

[Avio]

Thanks very much again. I figured too that both rotors and their drives are critically important. Always wondered how safe helos are to fly in, given that almost its whole safety depends on a few blades of flimsy, flexi, pieces of metal, all the while lifting insane weights and/or undergoing tremendous stress during some of the more heart-thumping maneuvers. Really enjoyed reading through your narratives on the maintenance. That one about the tail rotor gearbox failure, happened to me once virtually -- was taking off in the DCS Mi-8 and realized there was no tail rotor authority at all. Found out it was that my rudder pedals somehow was not picked up when DCS started. Plugging out and re-plugging solved that. One more reason for taking all pre-flight checks seriously   !!

 

[Sobakopes]

02.11.2021 в 15:24, AlphaOneSix сказал:

The overhaul time periods have nothing to do with how the aircraft is operated. They differ based on the part itself and who/how the overhaul is performed.

The components we pay most attention to are the ones that will kill us if they fail in flight. Tail rotor, tail rotor drive shaft, main rotor blades, main rotor hub, swashplate, that sort of thing. Nothing fails very often. I've been involved with a fleet of 10 Mi-17s for 15 years, and we've had two engine failures (both shortly after an overhaul) and one tail rotor drive shaft failure (caused by water getting into an oiled coupling). We also had a tail rotor gearbox fail in such a way that pedal inputs were no longer possible, which was caused by the failure to properly modify the gearbox at overhaul with updated internal parts. Other things have been caught during inspections that could have been a big problem had they failed in flight, but these things are quite rare. Usually things go bad slowly and are caught during scheduled inspections and replaced. Or the things that break don't result in the aircraft crashing, they're just a nuisance and are fixed as time and parts permit.

I've never seen an IFF antenna under the nose, only on the bottom of the tail. I suppose there could be two antennas, or I could be wrong and that's actually an antenna for something else. The one on the tail has always been the IFF antenna in my experience.

So what do mi8 staff think about its role as a gunship? 

[AlphaOneSix]

47 minutes ago, Sobakopes said:

So what do mi8 staff think about its role as a gunship? 

The best gunship is something that's designed to be a gunship. The Mi-8 isn't a gunship, it's just a truck full of rockets. Sometimes that's useful. I think it's better used for it's designed purpose...carrying stuff on the inside. But I've never been involved with using it as a gunship.

[Sobakopes]

2 минуты назад, AlphaOneSix сказал:

The best gunship is something that's designed to be a gunship. The Mi-8 isn't a gunship, it's just a truck full of rockets. Sometimes that's useful. I think it's better used for it's designed purpose...carrying stuff on the inside. But I've never been involved with using it as a gunship.

In game it's a great gunship... Until something starts shooting back. Really great rocket firepower but no armor. 

Edited November 5, 2021 by Sobakopes