Apache damage modeling

[arneh]

Crew protection from the side seems to be quite weak, thin windows, and the pilot seems to be sitting with almost his whole body up in the window...

 

That's not quite true, the seats have fairly thick kevlar armor along the sides up to about shoulder height. But the head is still exposed:

[Yellonet]

The pilot is a bit more exposed.

 

[arneh]

The pilot is a bit more exposed.

 

Well, I think the kevlar seat sides are movable, and that they would be more forward with better protection in a combat situation. Not entirely sure about that, but I have seen them in different positions.

[Yellonet]

Well, I think the kevlar seat sides are movable, and that they would be more forward with better protection in a combat situation. Not entirely sure about that, but I have seen them in different positions.

Yeah... that'd make you feel safe ;)

[Force_Feedback]

In Chechniya crew of struck mi-24s used to jump out with parachutes, some even at 200m after being hit by multiple MANPADS in an ambush near the base, and don't say it would be hard jumping out of an Apache, if it can be done from a Mi-24, then it can de done out of anything, especially if it has detcord running along the side transparencies ;)

Kevlar and .50 cal sounds like cardboard and CO2 guns...

[mimoshel]

My best greetings to the forum members!

 

I’d like to ask for a help if possible.

This is a passage from a fiction:

“Apache was no more then ten seconds in the nitrogen cloud when the acid haze began sparking furiously. The sparks killed the pilot flame already burning in the turbine, then, sparking more, relit the engine with a small explosion beneath the rotors. The pilot flame became a two-foot wildfire. <The pilot did not panic> When the rotor surged, he corrected for it. «I’ve got a hot start,» declared he calmly.”

 

What may the phrase «I’ve got a hot start» mean here?

 

Thanks beforehand.

[Force_Feedback]

That the turbine was already spinning at a sufficient speed for a relight.

[Sundowner.pl]

A Hot Start is a situation, when the fuel is lighten with insufficient air flow through the burner cans. Usually ends up with parts of engine blown away, or even melted. The turbine have nothing to do with it except it's usually have to be replaced :smilewink:

[mimoshel]

Hm...

Do I understand correctly that the situation may be described as the stoppage and restart (without cooling) of the engine?

[bradmick]

Not really, a Hot Start is pretty much solidly related to starting the engine. Its a condition where in either to much fuel is introduced at once with insufficient cooling air in the engine, an engine that has been operated and has a high temperature to begin with (hence minimum temperatures prior to starting an engine).

 

For example, the AH-64A's 701 engine has a maximum temperature of 965, but it has a start limit of 867. If it becomes apparent as per the chapter 8 checklist procedures that TGT will exceed this number prior to the engine reaching its idle speed, you are to abort the start. To do this, you retard the power lever of the effected engine to off, and turn the fuel switch of the affected engine off and motor the starter until its below 540 degrees if there is further evidence of combustion. After this you can attempt the start again after you've motored the starter a little more so that its below 150 degrees. If you attempt a start above this temperature, then odds are the temperature in the engine will exceed both 867 and the max of 965, which will cause the engine to melt (possibly).

 

Brad

 

bah...had to correct my EP's, I know the Deltas by heart, the Alphas not the same.

[mimoshel]

Well, I think that I'm beginning to understand.

But there is one thing that bewilders me.

The matter is, the machine is in the air and I don't see from the text that the engine has stopped. Is it so endeed? Did it stopped and then restarted? I can't imagine a start of a working engine.

(Excuse my stupidity).

[nemises]

it sounds to me that the Author is trying to say that this nitrogen cloud put out the turbine pilot light, but then a spark re-ignited it, and the backup of gas in the starter ignited causing the pilot light to give a burst of flame (like when your gas hob goes out and you relight it straight away, you get a puff of gas burning off).

 

No idea if that scenario is properly covered by the term "hot start", but from reading above, it sounds like it doesnt.

 

I mean, it's not like the pilot would shut down the turbines mid flight to get them under temperature ;)

[mimoshel]

I mean, it's not like the pilot would shut down the turbines mid flight to get them under temperature ;)

Yes, that is the point!

I thought "hot start" might just be a figure of speech meaning "nice beginning!" (ironically, of course) or something like this. But I am not sure.

[bradmick]

Hot Start is a bad thing. It means you've allowed the engine to exceed its maximums and proverbially 'cook itself'.

 

Yeah, it does sound like there was something that caused the engine to flame out, and then spark again. If the engine was running, and temporarily caused to flame out, but fuel was still being dumped into the hot section (coincedentally we don't put the rocket pods on the inboard pylons because it runs the risk of flaming out or stalling the engines) then all of that fuel would immediately combust and that'd make for a bad day. Overspeed, long thing of flame out the engine, etc..etc. Definately a bad day.

 

Brad

[mimoshel]

I think, I got it.

 

Great thanks to everybody!

[Force_Feedback]

Does anybody know the ballistic rating for the Ah-64's side panels? I'd say no higher than US class 1A? If it's classified or twitchy, then don't bother giving hints, I just can't believe the canopy of an F16 gives more protection than glazing of an attack helicopter.

Really scary that 37 grammes of explosives (1/3 of an expensive cell phone) can entirely shatter the glazing of such an acclaimed chopper. Surely the transparencies were designed to mitigate blast waves in some way. I know ballistics and high velocity shockwave balistics are two different things, but surely the designers could have anticipated that at least a small callibre HE round could have hit the helicopter dusring combat.

No chutes, only seat armoring, man, I have to envey those people that fly those things in combat zones more, respect. Interestingly, most helicopter crews during the Soviet Afghanistan war wore, and used parachutes. I don't know how well the Apache handles asymmetry of the main and tail rotor, but the Mi-8 and Mi-24 can tear itself apart due to the rapidly increasing resonance caused by missing rotor parts.

Oh, does the Apache have some kind of suspended ordnance blast protection (ok, it does not carry bombs like the mi-24 and -8 )? I remember reading of several occasions of mujahadeen getting a lucky shot into suspended FAB-250 bombs with the dshk and other large calliber machine guns...

[Yellonet]

Does anybody know the ballistic rating for the Ah-64's side panels? I'd say no higher than US class 1A? If it's classified or twitchy, then don't bother giving hints, I just can't believe the canopy of an F16 gives more protection than glazing of an attack helicopter.

Really scary that 37 grammes of explosives (1/3 of an expensive cell phone) can entirely shatter the glazing of such an acclaimed chopper. Surely the transparencies were designed to mitigate blast waves in some way. I know ballistics and high velocity shockwave balistics are two different things, but surely the designers could have anticipated that at least a small callibre HE round could have hit the helicopter dusring combat.

No chutes, only seat armoring, man, I have to envey those people that fly those things in combat zones more, respect. Interestingly, most helicopter crews during the Soviet Afghanistan war wore, and used parachutes. I don't know how well the Apache handles asymmetry of the main and tail rotor, but the Mi-8 and Mi-24 can tear itself apart due to the rapidly increasing resonance caused by missing rotor parts.

Oh, does the Apache have some kind of suspended ordnance blast protection (ok, it does not carry bombs like the mi-24 and -8)? I remember reading of several occasions of mujahadeen getting a lucky shot into suspended FAB-250 bombs with the dshk and other large calliber machine guns...

37g of explosives can do quite a lot, obviously depending on the type of explosive and how it is used, open air, closed in explosion, shaped charge...

 

Oh, and as long as US will continue to go up against underequipped and undertrained forces I guess protection isn't that high a priority.

[Force_Feedback]

Well, I was talking about the Strela-2 warhead, the rest is fragmentation, but still, 37g is like that small Belgian hand grenade, not that much, especially if you compare it to those 250kg bombs hung under the Ka-50 and Mi-24, ouch.

[Yellonet]

Well, I was talking about the Strela-2 warhead, the rest is fragmentation, but still, 37g is like that small Belgian hand grenade, not that much, especially if you compare it to those 250kg bombs hung under the Ka-50 and Mi-24, ouch.

Yeah, well... it's a plastic(?) window... :D

And what do you mean 37 g? There's a lot more in a Strela-2.

[Sundowner.pl]

I haven't seen listings of what type of protection each glass/acrylic panel gives, except the one between pilot and co-pilot/gunner, which is stated to withstand a direct hit from Russian 23mm.

 

Brad, do you have any info on this, or should we call the Boeing company ? :smilewink:

[Yellonet]

I haven't seen listings of what type of protection each glass/acrylic panel gives, except the one between pilot and co-pilot/gunner, which is stated to withstand a direct hit from Russian 23mm.

 

Brad, do you have any info on this, or should we call the Boeing company ? :smilewink:

The statement that "it can withstand a direct hit from Russian 23mm" doesn't really say anything, the speed of the projectile and it's type is obviously of high importance, more so than its calibre.

I'm pretty sure that window can withstand a direct hit from a 152mm shell. If you throw it.

[Sundowner.pl]

It actually say a lot. If an American brochure say about protection against 23mm rounds, that mean a 23x151mm 190g API-T and 188g HEI-T ammunition fired from AZP-23 water-cooled, gas operated cannon at 970/980 m/s of muzzle velocity.

[Yellonet]

It actually say a lot. If an American brochure say about protection against 23mm rounds, that mean a 23x151mm 190g API-T and 188g HEI-T ammunition fired from AZP-23 water-cooled, gas operated cannon at 970/980 m/s of muzzle velocity.

At what distance? And do you have a link for that definition of armor protection?

[Sundowner.pl]

No, I don't. That's the ammo and armament of ZSU-23-4 Shilka, and that's the system Americans feared the most. The AZP-23 cannon have a 2,5km effective range, but most typical test firing for testing armor are done at max 200m.

[Sundowner.pl]

I just got a reply from AH-64 Crewchief:

 

The acrylic panels are about 1/8 inch think and provide no ballistic protection whatsoever. The glass panels above and in front of the copilot are standard heated safety glass panels that provide minimal protection from things like bird strikes (or flying rocks) but also offer very little to no ballistic protection. The acrylic (transparent) blast shield between the pilot and copilot is 1.1 inches thick and is supposed to be able to withstand a 23mm hit. There is also a non-transparent blast shield between the pilot and copilot situated roughly below the transparent blast shield. Those two shields act to prevent the incapacitation of both of the crew if something explodes in one of the crew compartments, but it also protects the pilot from frontal fire. there are plenty of other ballistic panels built into the aircraft around the pilots, with most of it being the crew seats themselves, but there are also panels elsewhere, such as under the pilot's and copilot's feet.