Page 17 - Volume 11 Number 7

tube through the aft bulkhead and on to the static air of left and right ports was disconnected so that
instruments ... airspeed, altimeter, and vertical speed. Here is what’s happening.
As the wind blows the rain against the static ports, some water enters the plastic tubing until the tubing fills with enough water to prevent the wind from having any further effect. As the wind abates and the pressure it applied to the side of the fuselage decreases, that little slug of water tries to drain out. However, the capillary action associated with the small tubing causes some of the water to remain in the tube. As the slug of water descends in the tube, it causes a decrease in the tube’s pressure upstream of the water. This erroneously low static pressure causes the airspeed indicator to show some speed, since static pressure is less than pitot tube, ram air pressure.
Had Mr. Haines not noticed the discrepancy – or decided to depart anyway – I am quite certain that the problem would have corrected itself as the vibration and airflow of flight would remove the rest of the water. I admire his decision not to depart, however, with this never-before-seen malfunction.
The shop cleared out the water by blowing high pressure air into the static port on one side while having a tissue to collect the water that was expelled from the opposite side. I presume the portion of the tubing going to the instruments from the junction
there’d be no chance of subjecting the static system to too much pressure.
Well, I have an easier, quicker way to solve this problem – kiss your King Air. Actually, you are not really kissing it, but I hope no one sees you doing this because it’ll surely look like you are! Merely put your lips and mouth up over the static port – you may need a stool on the King Air – and lightly suck. Be prepared for a little water to be ingested. Do it to both sides and then recheck your airspeed indicators in the cockpit. Fixed it, didn’t it? No access panels removed, no tubing disconnected, no shop air needed ... just a little “kiss” and you’ll be good to go.
I bet that little tip was never covered in King Air ground school, was it?! KA
King Air expert Tom Clements has been flying and instructing in King Airs for over 44 years, and is the author of “The King Air Book.” He is a Gold Seal CFI and has over 23,000 total hours with more than 15,000 in King Airs. For information on ordering his book, go to www.flightreview.net. Tom is actively mentoring the instructors at King Air Academy in Phoenix.
If you have a question you’d like Tom to answer, please send it to Editor Kim Blonigen at kblonigen@cox.net.
JULY 2017
KING AIR MAGAZINE • 15