Rich
The breeze created by the open doors would play havoc with the blankets and any blanket that had faulty or worn snap fasters would flap about, make noise and could cause damage to the transmission island panels and structural bulkhead and would damage the blanket, the skin was only .008 inches thick!
The major reason behind missing or lost soundproof blankets was that although they were coded as "Unit-repairable" in the parts manual, neither the (TM 55-1520-210-20) or the general aircraft maintenance manual (TM-55-1500-204-25/1) informed the guys on how to go about repairing them. So if they came loose it was easier to just remove them.
(Boring bit for us detail lovers )..
Replacing a soundproof blanket (NSN -5640-00-269-1048) was costly, a large blanket was over $100. Buying in bulk, a square yard would cost $5.90.
Incase you have ever wondered, this is how the blankets were attached inside the huey. The transmission and bulkhead was covered in screws known to the maintenance guys as "Studs". On the outside of the blanket was a snap fastener cap, which would be attached to a snap fastener socket on the inside of the blanket. The snap fastener socket on the inside of the blanket would then clip onto the "Studs" on the transmission and bulkhead to hold the blankets in place.
Weight was an issue, raised density altitude caused by the heat, was a big problem in Vietnam and not just for the fully laiden gunships that had to bounce down flightlines to get into the air. Many a slick was lost in an LZ desperatly trying to maintain a hover.
Which brings me back to the Nighthawks. The Nighthawk was the most heavily armed slick in any unit in Vietnam and although (due to its name) it was perceived by most,as nothing more than a nightime perimeter guard or a spotter for gunships (The Fireflys job) It had a far spicier role in Vietnam. Its size and armament didnt go unnoticed by special forces and due to the fact that it could carry a few troops and had a fare amount of fire power, The Nighthawk was used to insert Ranger/SOG/Seal units into places that a slick and gunship escort would bring to much attention. Dak To was a favorite forward base for SOG recon missions, They would use a single Nighthawk to drop them over the border into Laos to gather intel on the Ho Chi Minh Trail. The Nighthawk had the firepower to help out if things went pear shaped and would often be sent back to pick the guys up at the end of the mission.
With the armament and amount of ammo that needed to be carried on a Nighthawk and with the prospect of carrying a team of guys behind enemy lines without a wingman or escort, it makes sense that any Nighthawk CE would choose to reduce as much weight as possible. If the doors are open, they may aswell be off! With the doors off, who needs the added agro of flapping soundproof padding! Plus it may just save on a little weight!
(Phew)!! i hope that helps explain things a little.
Andy
While the rest of the crew may be in the same predicament, it's almost always the pilot's job to arrive at the crash site first.