Page 12 - Volume 11 Number 4

The King Air
Cabin Door
by Dean Benedict
Ijust wrote about the cabin door in the February 2017 issue of this magazine, but I thought of a few more points I could make on this topic.
To summarize briefly where I left off: If a King Air has a cabin door squawk, nine times out of 10 it is going to be the door warning light on the annunciator panel coming on when the door is properly secured. The warning light is triggered by switches. All King Airs have two switches in the door frame and one switch in the door handle inspection light hole. Newer King Airs, plus many 300s and 350s, have two additional switches, one at each upper door hook. If one of these switches fails, you get that warning light. A bad switch is the most common reason for a door light when the door is closed and locked.
Obviously, if you get a light on the ground, you aren’t going to take off until you verify the door is properly closed and the light is extinguished. It could be that the door wasn’t properly latched, or it could be a bad switch. If everything looks good on the ground, but you get a cabin door light on the annunciator panel after you are airborne, the chances are your door is fine and you have a switch going bad somewhere in the system. This assumption is based on my experience with King Airs over the last 40-plus years.
Warning Light in Flight – What to Do
The POH addresses the subject as follows:
Illumination of Cabin Door Warning
Warning: Do not attempt to check the security of the cabin door. Remain as far from the door as possible with seat belts securely fastened until the airplane has landed.
1. If the cabin door warning annunciator illumi- nates, depressurize cabin (consider altitude first) by activating cabin pressurization dump switch on pedestal.
2. Do not attempt to check cabin door for security until cabin is depressurized and the airplane is on the ground.
3. Check security of cabin door (on the ground) by lifting the cabin door step and checking position
An extended King Air cabin door. When the door is open, the handle is below the bottom step; when the door is closed, the steps fold down out of the way and the handle is at the top of the door inside the airplane.
of arm and plunger. If unlocked position of arm is indicated, turn door handle toward locked position until arm and plunger are in position.
Furthermore, the placard next to the handle is pretty clear: “Do not attempt to check security of cabin door by moving door handle unless cabin is depressurized and aircraft is on the ground.”
What Not to Do
Should you get a cabin door warning light in flight, don’t touch that door handle! Many years ago, a pilot got a cabin door warning light during flight and his co-pilot left his seat to check the door. Apparently, he grabbed the handle to see if it was locked, but turned it the wrong way! Since the aircraft was pressurized, the door flew open and the co-pilot was sucked out of the aircraft. The pilot declared an emergency, made his descent and landed. Of course he assumed his co-pilot fell from altitude and was fatally injured. Imagine his surprise when he discovered the co-pilot had managed to grab hold of the door cable, held on for dear life, and lived! Astonishingly, he was not seriously injured (at least not physically). Reportedly, the biggest problem
– Part Two
10 • KING AIR MAGAZINE
APRIL 2017
MAINTENANCE TIP