SUMMERTIME GOTCHAS

Those lazy, hazy days of summer are upon us and with each season, a few “flying gotchas” peculiar to that time of the year lurk in the shadows. We cannot address all of them, but here are a few that have resulted in recent accidents and incidents.

We all know that the knee bone is connected to the thigh bone, the thigh bone is connected to the hip bone, and the pitot tube is connected to the airspeed indicator. If the pitot tube is blocked, the airspeed indicator will sit happily on zero as we charge down the runway during a takeoff. If we take our first glance at the airspeed indicator just as we sense that we have accelerated to our rotation speed and observe zero airspeed, we have an urgent decision to make. Do we abort the takeoff and hope there is sufficient runway remaining to stop the airplane? Or do we rotate and rely on control feel and correlation with other flight instruments to get ourselves safely back on the ground without a direct airspeed reference? Let’s not ever get ourselves in that position and here is how we can do that. A check of the airspeed indicator early in the takeoff run will reveal any problem. Resolving to always make a verbal callout, “airspeed alive!” when we sense we have reached about thirty knots should allow us ample runway remaining to stop and get the problem resolved by a maintenance technician.

Ensuring that the pitot tube is not blocked is good practice year-round, but warm weather brings out a creature that has a great affinity for the pitot tube. The mud dauber wasp loves airplanes. Airplanes have small openings that are perfect for building nests and laying eggs. That includes pitot tubes and fuel vents, the latter of which can cause engine power loss due to fuel starvation if a vent is plugged.

Another “gotcha” can be summer allergies or the meds that might be taken to relieve symptoms. Our fitness-to-fly is always a consideration and we all know about the venerable IM SAFE checklist. Allergies or our attempts to control them can flag two items on that checklist, illness, and medications. Many allergy medications, both prescription and OTC, can be significantly impairing and do not mix well with aviation fuel. Diphenhydramine, the active ingredient in several popular allergy medications, has been the subject of NTSB and FAA scrutiny.  The FAA’s Guide for Medical Examiners¹ lists a wait time of 60 hours after the final dose of a medication containing diphenhydramine. That guide also contains much useful information regarding many other medications.

True or false, “ice is not a problem in summer.” False! That is a frequent “gotcha” for pilots who fly airplanes that have carburetors. Many things grow well in the summer and that includes carburetor ice. The venturi effect in the carburetor, coupled with the vaporization of the fuel, can drop the temperature in the throat of the carburetor by as much as 70 degrees Fahrenheit. A hot and humid summer day with a temperature and humidity squared at 85 degrees Fahrenheit and 85 percent relative humidity can be a real ice maker. It will not produce enough ice for a party but can make enough ice to spoil our party in a big way. As the warm, humid air is cooled from 85 degrees F. down to about 15 degrees F., ice forms in the throat of the carburetor and around the throttle plate. The result can be a reduction of engine power leading to a complete power loss if the situation is not detected and addressed promptly. There is much more to say about carburetor ice and the use of carburetor heat. Check out Chapter 7 of the FAA’s Pilots’ Handbook of Aeronautical Knowledge.

Some people enjoy the summer heat and others dislike it. If we personify our airplanes, they fall in the latter category. Airplanes are not fond of warm days and they show us that by being rather lethargic. We all know that as the air temperature increases, the density altitude also increases, and the airplane performance decreases. Sometimes pilots forget about that and a “gotcha” awaits. That pleasant little airport with the short runway and trees at the end was great fun to visit in early April. The departure was fine with sufficient room to clear those trees.  A return visit in July or August might not work out as well. Seeing a windshield full of trees while running out of room to climb above them during a hot day takeoff is not fun. It is also not a good time to think about checking the performance charts for the takeoff distance. Planning is the key to success at many things in life and flying, particularly taking off, is one of them. 

¹ Guide for Aviation Medical Examiners (faa.gov) 

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