# Why does the UH-1 Huey have a hump at the rear of the cabin?

Why does the Huey have this weird hump as shown in the picture? For some system? Why not remove it?

• Because the main rotor shaft and associated equipment (gearboxes) does not end at the outer fuselage skin. I am sure someone more versed in the arcane version numbers of the UH-1 will be able to weigh in regarding when the area around that "hump" was made available. – AEhere supports Monica Feb 18 at 8:43
• @AEheresupportsMonica Comments are not for providing partial answers. – bogl Feb 18 at 9:20

A copy of the original image can be found here, which is about 5 'pagedowns' down this page, which has a number of other excellent Huey-model photos.

It's a bit of structure to guide the rotor forces into the rest of the airframe, it would not be good if this bit went missing.

Fwd/aft, left/right, up/down. The rotor provides the lifting forces and driving forces and these are quite concentrated around the rotor axis. Picture the airframe like an empty beer can - some panels are required to cope with the forces while remaining in shape.

• Nice model. Yours? – FreeMan Feb 18 at 14:51
• @Freeman found it while searching for a structural image for the Huey, seems to be unclear if the original site still exists. Could not find a clear reference address for it. – Koyovis Feb 18 at 23:20
• Providing a source for the image would be strongly recommended, then. – FreeMan Feb 19 at 15:31

It's where the main rotor transmission and control servos are housed. The forward bulkhead of the "hump" WAS the entire aft cabin bulkhead of the original Huey models. Starting with the D model (I Think) the cabin was extended around the transmission tunnel to form what are called the right and left alcoves. The original shorter body Hueys were adapted to the gunship roles.

Click to view, cropped from https://forums.eagle.ru/showthread.php?t=98895

The biggest feature in that area is the fuel tank, which is roughly 0.65 m$$^3$$ (165 US gal). With a cabin height of 1.2 m (it's not a standing cabin), the base (assuming square) would be 0.74 x 0.74 m (2'5" x 2'5") of floor area, which does look right.