December 2018 Issue

Air In The Tanks

Just read October’s Learning Experience entry, “Air In The Tanks.” This account has two lessons that weren’t expanded upon.

I’ve owned Cessna T210s since 1977; first a 1969 J model and then a 1979 N model with a TSIO-520-R engine. In the 1980s, there were a number of fuel exhaustion accidents in 210s, all of them attributable to not getting a full fill and resulting in being shorted an hour’s supply when fueling stops after fuel backs up out of the filler port. The outboard sections of the fuel tanks are slightly higher than the bottom of the filler port. To get the last one-plus gallons in the tanks requires the slowest of fueling until reaching the real full point.


I determined the real full point when calibrating the JPI 930 in my 1979 N model by starting from empty and adding fuel in five gallon increments until getting to the factory-claimed 44.5 gallons of useful fuel. At the same time, I calibrated a fuel stick to mark the same points up to full. The full point was halfway between the bottom of the filler point and the upper ring in the neck of the port.

Unless instructed or learned from experience, I repeatedly find fuelers don’t know where the full level is and stop fueling once fuel splashes out of the filler port during high pumping volumes, leaving the tanks easily eight to 10 or more gallons below a full fuel load. Anyone unaware of this can make the mistake of flying to a 45-60-minute reserve only to find out the fuel isn’t there and having a fuel exhaustion event just as the destination is reached. Further, my standard practice when planning to fly more than 3.5 hours is to stick the tanks to get a true measure to determine if each is really full.

The second issue is calibration of the fuel flow transducer required to get accurate fuel usage data. The transducers have a value used to program the instrument for fuel flow. The instrument’s out-of-the-box value may or may not be accurate for a particular transducer. This seems to be true for original installations as well as replacement transducers. Knowing the fill point for the tanks, data on fuel used needs to be kept per instrument versus the amount needed to reach the true full fuel load. Over time, the data will determine the accuracy of the fuel flow instrument, and an adjustment can be made to get the most accurate fuel usage data. Once known, aircraft logbook should get an entry noting the value so the process doesn't have to be performed again in the event a transducer is replaced with the same part number.

This kind of information is available on the Cessna Pilots Association web site, should be known by CFIs really familiar with Cessna 210s and should be taken into account by anyone flying a 210.

Eric Woodman

Via email

Thanks for filling in those gaps. Knowledge like this is the best recommendation we can make for type clubs. With that in mind, the late John Frank, long-time president of the Cessna Pilots Association, had this to say about the 210’s fuel tanks: “Because the fuel tank is long and flat and has a recessed filler port, it can be difficult to get the last few gallons of fuel in each tank. The tank may appear full when it is actually 5 to 10 gallons short. There have been a number of off-airport landings caused by fuel exhaustion because the pilots thought the tanks had been filled but were actually short of full by a significant amount.” The same basic problem is going to exist among aircraft with similar wing dihedral and tank design.


Proactive ELTs

Following up on the ELT article in October 2018’s Aviation Safety (provocatively titled “ELTs”), one of the advantages of the 406 MHz ELTs is that it only takes a few digital bursts to determine a location of a possible crash or off-airport landing.

We all have heard that ELTs have not been reliable transmitters after an actual off-field landing or crash due to breaking off the antenna or its coax cable, the G-activation switch did not work, the aircraft flipped over, etc. There is a very easy solution that I have not seen mentioned—turn on the ELT while still in flight in addition to squawking 7700. All it takes are a few 406 MHz bursts for the satellites to pick up the distress signal.

Also, tell your passengers to activate the ELT switch if it appears that there is a serious issue at hand. Turning on an older 121.5 MHz-only ELT in flight would not be very helpful since the signal will not reveal the location as would a GPS-equipped 406 MHz device heard by a satellite.

Separately, I have heard comments among pilots that ADS-B Out will eliminate the need for the ELTs. Undoubtedly, a good trace of the flight path of an aircraft will help in search and rescue, but not necessarily imply a quicker find. The aircraft still needs to be declared missing, something that might take a few hours or a few days, especially aircraft not on a flight plan.

Luca F. Bencini-Tibo

Weston, Fla.

A timely comment, given Mike Hart’s article this month on SAR communication realities. See page 4 for more. Thanks!


Engine Failure Risks

Excellent article by Bob Wright on engine failures and risk mitigation strategies (“The Real Risks Of Engine Failures,” November). I would like to add two more: Avoid intersection departures and request full-length takeoffs whenever possible.

At many airports with long runways, it’s often customary for the tower to offer intersection departures, and many times it’s not to facilitate traffic but to minimize taxiing time. If an engine failure occurs at or shortly after rotation, landing straight ahead on the remaining runway is an option I would not want to give up.

Terrain awareness is another risk-management strategy. Get familiar with what lies beyond the departure end of your runway(s) using satellite images from Google maps, develop a plan for an off-field emergency landing and commit it to memory (i.e., a nearby clearing 30 degrees off runway heading).

Spiros Hatiras

Via email

Excellent points, thanks! We’ve long maintained that a takeoff is riskier than a landing, because the airplane is accelerating instead of slowing down, and because it’s not yet demonstrated that the airplane will fly. Using all the available runway and knowing what’s beyond the trees at the far end expands your options and are two great ways to help mitigate the risks that exist.