|MD80 Standby Compass|
Have you ever been in the cockpit of an MD80 series aircraft? If you have, then you probably weren’t able get over the scrambled and chaotic design of the cockpit long enough to notice that something important was missing…the standby compass.
I learned to fly in a 1980’s era Cessna 152 with a compass located in clear view in the center of the instrument panel. The compass had to be checked against a standby “wet” compass and manually corrected by the pilot every few minutes. If the pilot forgot to make the necessary corrections, then the compass would develop an error over time that would eventually lead the aircraft off course. Most modern aircraft are equipped with a slaved compass system that continually and automatically updates and corrects the heading information displayed on the cockpit instrument panel, removing the need to continually check the accuracy of the compass system. A standby compass is still required equipment and must, at a minimum, be checked before each flight and would be used in the event of a failure of the slaved compass system.
The cockpit picture below is that of a Boeing 757-200. The standby compass is prominently and conveniently located on top of the center window post. In the event of a failure of the compass system on this aircraft the pilots would be able to easily and clearly view the compass. Except for the light within its casing, the standby compass needs no electrical power to operate and is functional during a complete loss of electrical power.
|Boeing 757-200 Cockpit|
The cockpit picture below is that of a McDonnell Douglas MD83. Now that I’ve mentioned it, you might notice the absence of a standby compass. Clearly this aircraft does not have a center window post, but it seems logical to me that the compass could have been placed above the post nearest the Captain. If that wouldn't work, I could come up with at least two or three other options...in the ceiling behind the First Officer would not be one of them, but that's exactly where it is.
|McDonnell Douglas MD83 Cockpit|
In order to view the standby compass on this aircraft, the pilot must first flip up one of two mirrors on top of the instrument panel…one for the Captain and one for the First Officer. No, the mirrors are not for checking the condition of your hair, but they are probably used more often for grooming tasks than for checking the compass.
After flipping up the mirror, the pilot must position the mirror in just the right position so that he can see a second mirror in the ceiling in order to view the compass. The second mirror makes it so that the compass is not viewed backward as it would if viewed through only one mirror. There’s even a light switch on the overhead panel that turns on a small light to illuminate the face of the compass.
The video below shows the procedure in full. After viewing the pictures and video maybe you will have the same thought that I’ve had for years…I sincerely hope I never have to use it on a dark and stormy night.