Page 20 - March23T

a maintenance crew removed all the protective covers to perform engine runs and neglected to reinstall the cov- ers. On the takeoff roll, the captain’s airspeed indicator showed zero knots and only started “working” when they were airborne and climbing. What the captain thought was airspeed was actually the sea-level air trapped in the pitot line expanding against the now-decreasing static air and giving the false indication of positive pressure coming into the pitot tube. Several wrong assumptions later, the airplane crashed into the Atlantic. The pitot tubes were never recovered, but the most likely cause is that a mud dauber wasp built a nest inside the perfectly cylindrical tube.
In the case of Aeroperú 603, the crew neglected to find tape that covered some or all of the airplane’s static ports. The aircraft was washed before the flight and the ground crew didn’t remove the tape. The aircraft took off after midnight from Lima, Peru. The combination of erroneous airspeed and altitude indications and a lack of ground references on a dark night over water caused the aircraft to crash into the ocean.
When performing your preflight inspection, look inside the pitot tube for obstructions, preferably with a flash- light, and also look at the vent hole(s) on the outside of the tube to make sure there aren’t any clogs. If you see something inside the tube, unless it’s right on the edge
of the opening and you’re sure it’ll come right out, call a maintenance tech. People have tried to dig things out of pitot tubes only to end up packing them like a Civil War musket. If you accidentally shove something into the pitot tube, tools, testing and invoices will likely be involved before you can go flying. It may look like a simple thing but remember that anytime even one fitting is loosened on the pitot/static system, leak checks and functional tests must be accomplished.
I know I don’t need to say this but humor me. Pitot tubes are not grab handles to use to get a good look inside the nose gear well. My knees hurt too, but please find a different way to brace yourself. Another pro tip from the “been there, got the scars” file: It only takes once to grab a hot pitot tube before you’ll forever lightly hit the tube with the back of your fingers before touching another one. I’ve done the “that might be hot” smack to a pitot tube that was lying on my toolbox before picking it up.
All the same advice applies to static ports. You typi- cally can’t see very much in there, but it’s good practice to take a look anyway. On RVSM-certified aircraft, it’s important to keep the “RVSM critical” area around the static ports and pitot tubes clean because contamination or deformation in these areas can cause erroneous indica- tions. Your aircraft’s AFM or POH should have a diagram of where the RVSM critical area is. Otherwise, contact the
Cessna
Plug & Play All the Way!
NEW for Twin
LED Caution Advisory Panels & Gear Status Lights
Cessna 340/340A, 401B, 402A/B/C, 404, 414/414A, and 421A/B/C models
• LED Reliability & Lighting Performance
• Drop-in Plug & Play Replacement
• New Cable Harness & Connector included
• 16, 18, & 22-Station Configurations
Luma
http://luma.com
• Ten Year Warranty
LED Gear Status Display (Single modular unit)
18 • TWIN & TURBINE / March 2023