Reliability Calculations for two Aircraft hangar doors

Project Info


Our company was requested the mechanical analysis of an aircraft hangar Bi-fold and Quad-fold doors.

The size of the doors was 6mx6m with 20mm thick glass panes.

The static analysis of these doors was already completed for in-service wind loads, dead loads, etc. We were requested to follow up the following analysis:

  1. Motion analysis of the door. Due to fire and emergency regulations when the door is closed and the power/electricity is cut, the counter-weight is to be just heavy enough to allow the door to open on its own in less than 60 seconds. When the door comes to its final opened position the door is not allowed to have a heavy impact that breaks the glass, a suitable damper is required to slow the door into its final position.
  2. Analysis of the drive motor to ensure the motor will run sufficiently. Doing sample calculation for peer review and certification purposes.
  3. Check/analyze the gears and drives and providing sample calculation for peer review and certification purposes.


  1. The doors were supposed to resist against rain, snow, cold weather condition and frosting of its parts.
  2. The design was to be modified in a way that it could easily move during the entering and exiting of the aircraft from the hangar without installing any rail or frame on the ground.


In order to guarantee that all the requested features and requirements were properly considered, we modified the existing design and made all needed calculations to check the final design.

Some of the main features of the door included the followings:

  1. The door could be folded up and down without any need for a frame on the ground.
  2. The door could open automatically when the electrical power was cut off
  3. The door needed the minimum maintenance and a reliable mechanism to work for a long time without the need for a physical maintenance. In order to achieve this goal, all hinges and buses were considered to be made up of Teflon with a suitable tolerance so that heating and cooling due to environmental changes would not have an adverse impact on them such as jamming in the cold weather.

We put a rotational damper on the counterweight sheave to reduce the falling speed of the counterweight and folding up the leaves to complete its movement according to the 60 seconds requirement.

Based on the result of our calculations we advised the following damper from KINETROL

damper from KINETROL



The project took about 3 weeks to get completed and was later checked with the client. The work suggested improvements on such components as the damper, counterweight, and the motor for both the bi-fold and quad-fold door. The design was then submitted to the client for the manufacturing.

B. Hutchinson
May 14, 2018
Mechanical Engineering