How do you model a slightly damaged chopper?

From a historical point, and I am no expert, the crew probably wouldn't have left the aircraft intact.  At least now, and from my time flying the UH-60, if it is likely that the airframe could be captured it is standard procedure for the crew or a recovery team to destroy the aircraft well beyond use.  I'm no expert though, and things might have been different then.  Also, you'll want to do plenty of research.  You may have to stratchbuild detail that would show through the damage.

  To answer the bulk of your question:

1)  Dents:  I have utilized, and be very very careful, a dremel with an engraving tip.  Lightly touch the surface where the dent will go and sand the edges smooth.  The same, and safer, can be acheived using a No. 11 blade in place of the dremel.

2)  Bumps:  Not really sure what you mean here. 

3)  Small Parts Torn off:  Utilize your references with this one.  Some parts are more easily damaged and torn off than others.  Antennae's are a good example.  The cable cutters on the top and bottom of the aircraft, above and below the pilots, are an example of items that are designed to be very tough and wouldn't be easily damaged (unless they actually strike a cable). 

4)  Burn Marks:  I find it best to use artist chalk (not oil) pastels.  Simply rub the pastel stick on some sandpaper to grind it into a powder and using a brush, an old one since it will be virtually destroyed due to the sandpaper, apply it to the area to be burned.  Dark greys, black, browns, and even white (sparingly) can be used.  Best part is if you don't like the look, simply wipe it off with a soft rag and some water.  If you have an airbrush, you can thin similar colors of paint (as the pastels) more than usual to make them more translucent.  Apply a little at a time. 

Hope it helps!

In addition to the great advice above, I would suggest finding a pics of downed helos and modeling one similar to what you see.  Sometimes (rarely) helos were left in place when damaged, but as stated,  were usually destroyed in place if they could not be recovered.  

Here is one I did of a downed Navy Seawolves UH-1C (sorry for the crappy pics, I hade a crappy digicam back then).

Good luck.

Wow! I only sent my message this afternoon; the speed, efficiency and authority of the replies I receive on FSM every time I post something is amazing. Thank you Brian and Gino P your answers are very helpful. I take note of what you say about crews not wanting to leave their machines anything near intact for the enemy to find. In modeling there is nothing wrong with being unhistorical  - take, for example, models of Luftwaffe aircraft that never left the paper they were designed on, the so called Luftwaffe 1946 - but personally I like to keep to historical accuracy if I can. So if I want to do a diorama where the Viet Cong come across a downed heli then I'll rough up the heli a lot. Alternatively, perhaps I'll think it is a pity to 'damage' the model that much and just build it OOB but with some weathering worthy of the jungle, and its US crew manning it. Another idea would be a damaged chopper but safe in its base. By the way, the Viet Cong figures I have are not from Academy as I said previously, but from Dragon.

I wonder did you Gino use the same model in your diorama as the one I've got? Mine is Academy's 1/35 UH-1C Huey "Frog".

Ffowcs

I did use one of the Academy UH-1C kits, I don't remember which one it was though.  The plastic is basically the same in all the different boxings.  The only differences are the decals and some include weapons that the others don't.  The "Frogs" boxing has all the weapons included in the other kits.

Here are some examples of crashed Hueys.

They tend to roll on their side when the taol rotor and main get out of balance.

By the way, I disagree with this statement:

"In modeling there is nothing wrong with being unhistorical - take, for example, models of Luftwaffe aircraft that never left the paper they were designed on, the so called Luftwaffe 1946..."

I don't see the point in the fictional Luft '46 or Paper Panzer crap.  Its all Sci-Fi if you ask me.  I stick to building historically.  To each their own though.

Not a problem.  Happy to help!  I'm sure there have been instances that the crew or recovery crew weren't able to destroy the airframe before the VC came along.  Besides, if you're happy with it then it's just fine.  No rivet counting here!  Just post some pics when you're done!

Many thanks for the photos. They help a lot. Maybe I'll buy a second Huey, do one as whole and the other as damaged. It would be good to build an example of both.

I agree with you with buidling historical subjects. Despite what I said, and sounding like I was a fan of fictitious subjects for modeling, I am not in fact - and have never modeled a Luftwaffe 46 or anything like that. As you say, each to his own but always historical subjects for me as well.

I'll post photos of my build in this Forum. But may be a while yet.  

Lots of good info above. Based on photos of the Vietnam War and what I have read, I would speculate that downed helicopters were not often destroyed, but were recovered for rebuild whenever possible. One reason being to administravely say an aircraft was damaged, rather than destroyed and on paper reducing total losses. The same airframe theoreticly being capable of being rebuilt downed and recovered repeatedly if it did not burn completely.

Here are a few more downed and recovery pics from the battle of Ap Bac.

I remember the beginning of Dog Soldiers, I think, where the tails of downed choppers were shipped back to the US so that the tail number was not a strike off. And yes, I know it was a novel, just saying. Still, 3,000 plus were lost, so it's probably safe to say you can set up your dio just about however you want. A good way to model really damaged metal is tin foil. You can burnish a piece down over the plastic part and it'll pick up every detail.

Then paint it and place it in the model. It's hard to handle without budging it up, but smaller pieces help. Particularly for what you are doing, the give away is the edges of stuff, so build them out with thin material. I like beer can aluminum too. I make my landing gear doors and such from it.

you could have the heli damaged enough that all crew were killed (as gruesome as that sounds)? or how about stuck high up in the trees?

a few ways for damage;

grind away a panel and replace it with kitchen foil. dent it and then backfill it with resin to hold its shape and paint it.

heat with a candle and press the plastic in (takes lots of practice to get this technique to look good)

drill out the back side of panel with a dremel until extremely thin, then punch holes through with your hobby blade.