Hi, I’m Bruce Landsberg and welcome to the Leading Edge. We’ll discuss safety-of-flight issues, procedures, techniques, and judgment. With the convective nature of Internet misinformation, and so much content that is over weight and out of balance, you need an experienced and trusted source. So, strap in and let’s go fly!

Big Watches, Fuel Gauges, and Annunciator Lights

November 24, 2015 by Bruce Landsberg

The notion that engines run on air is no more absurd than attempting flight with insufficient fuel in a tank connected to the engine. Yet hardly a week goes by that somewhere a pilot is attempting to go where none have gone before.

The technology of measuring fuel has gotten much better than the wire and cork device used on the Piper Cub. The Cub’s design was stone simple—mount the fuel tank directly in front of the pilot (not such a great idea from a crashworthiness perspective, but only a short hose run to the engine) and attach a cork to the end of a wire rod. The length of rod protruding through the fuel cap indicated how much go-juice remained. Only two things could go wrong: The cork could become saturated and sink, giving the pilot a sinking feeling that no fuel remained, or worse, the rod could become slightly bent and jam, falsely indicating more fuel on board.

We paid little attention to any of that and always used our big pilot watches to determine how long to stay aloft. Time is one of the best indications of what’s left in the tank(s), provided you know what was on board to begin with and are familiar with the engine’s burn rate—both highly recommended procedures.

New pilots are often told that the fuel gauges on light aircraft are unreliable and that the FAA only requires them to be accurate in one condition—empty. Let’s dig into that a bit more. As usual, there seems to be some gray!

Under CAR 3.672 Fuel Quantity Indicator, the Civil Air Regulations by which most legacy aircraft are certificated, “Means shall be provided to indicate to the flight personnel the quantity of fuel in each tank during flight…Fuel quantity indicators shall be calibrated to read zero during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply as defined by § 3.437.” [ital. added]

Under the new regs, FAR 23.1337 Powerplant Instruments Installations—(b) Fuel quantity indication, “There must be a means to indicate to the flightcrew members the quantity of usable fuel in each tank during flight. [ital. added] An indicator calibrated in appropriate units and clearly marked to indicate those units must be used. In addition: (1) Each fuel quantity indicator must be calibrated to read ‘zero’ during level flight when the quantity of fuel remaining in the tank is equal to the unusable fuel supply determined under § 23.959(a)…” It’s not appreciably different from the earlier rule.

It could be reasonably argued that quantity indications should be accurate but sometimes the hardware is suspect. The FAA goes on to say in a safety publication, Time in Your Tanks—P-8740-03, “Fuel gauges are subject to malfunctions and errors. Therefore, unless restricted by the gross weight or center of gravity limits, it is considered good judgment to ‘top off’ the tanks at fuel stops. If the fuel load must be limited, you should endeavor to get an accurate measurement of fuel quantity by using a dipstick calibrated for the aircraft.” Dipsticks are a good measure…IF…they are properly calibrated…AND…the aircraft is sitting level, which allows Murphy’s law to slip in.

With the “rebirth” of GA in the ’90s, most manufacturers added low-fuel annunciator lights to new production aircraft (a.k.a. fuel “idiot lights”—they have been installed on most automobiles and larger aircraft for decades) separate from the gauging system to make it really hard to run the beast out of fuel or a tank dry. In general, it’s worked very well although one young CFI and his student managed to run a new production Cessna, equipped with lights, out of fuel. No need to belabor the point where I’m sure both participants will do better in the future. The fuel accident numbers of new tech aircraft compared to the classics is much better and it’s not because pilots suddenly got smarter.

But suppose you own a classic, and installing annunciator lights is prohibitively expensive. A highly recommended upgrade, second only to installing shoulder harnesses, is to install a fuel flow transducer/totalizer which will accurately measure fuel flow to within a few tenths of a gallon. As for quantity, it must be properly programmed, so it’s not quite as goof-proof as the low fuel lights. Used on every flight, it provides great peace of mind—either more fuel is required or it isn’t. As far as not running a tank dry, a timer or that stopwatch function on your chronograph or some other clock on board should help.

Back to the FARs—Do the gauges need to be accurate or not? In my view, it’s irrelevant. The Air Safety Institute’s “Golden Hour” approach of always landing with one hour of fuel on board elegantly solves the problem.


Bruce Landsberg,
Senior Safety Advisor, Air Safety Institute

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The science of building/maintaining aircraft

November 11, 2015 by Bruce Landsberg

young mechanic (1)

Building and maintaining aircraft is mostly science and perhaps a bit of art. There should be a keen awareness on the tradeoff made between affordability, suitability, and safety. If it’s a homebuilt and you built it, than who knows better than you on how to maintain it? That’s somewhat debatable and while the amateur-built regulations give us plenty of rope with which to hang ourselves, there are some best practices that should be taken as gospel. Many have been learned the hard way.

A few observations:

Hot Seat—Understanding amperage, circuit breakers, and good wiring technique is more than just a good idea. A homebuilt flying the Everglades some years ago in visual conditions asked ATC if they were aware of any fires in the area. ATC knew of nothing, but the pilots soon discovered that the automotive electric seats they had installed had turned into hot seats. Unfortunately, the plunge into the swamp was fatal and the NTSB noted that a circuit breaker supposedly protecting wiring and accessories from a short circuit, didn’t. We can discuss the wisdom of electric seats in homebuilts but wiring practices are really non-negotiable. It was high price to pay for a bit of ignorance.

Hose Clamps—Another fatal accident occurred when a mechanic decided to use an automotive hose clamp to secure a muffler and exhaust pipe on a Piper Cherokee, resulting in an in-flight fire. The aircraft version, while about 15 times more expensive, had a critical detail that the mechanic apparently overlooked or thought unimportant. There is a pin on the clamp, which is inserted into a hole in the muffler and exhaust pipe and holds the two together even if the clamp loosens. Some parts of aircraft really do need to be expensive and well-made.

Plumbing—A recent honest mistake apparently involved the builder of an RV-10 who suffered an engine stoppage due to fuel starvation. There is currently a $35 million lawsuit pending against Vans Aircraft and the manufacturer of the fuel flow transducer that the NTSB reported was plugged by an improperly-used sealant in the system. There was loss of life so the legal system is involved. Sometimes that’s warranted but this has little, if anything, to do with Vans in my view.

There is a long thread on Vans Air Force that looks at the pros and cons. One of the writers thoughtfully points out that there is perhaps not enough guidance on what and how one should specifically assemble various parts and pieces. In my two earlier examples, it seems the guidance was pretty clear and the crux of this suit may hinge on what the builder knew and when he knew it. How much guidance should a manufacturer for a kit or a component provide, and does that incur additional liability? Is it their responsibility to educate builders on everything that a certificated mechanic should know? Guess a jury will sort that one out.

One thread respondent points out that in too many cases there is “tribal wisdom” or the excuse that if the Framistan hasn’t failed in 350 hours it must be done right. Perhaps, but there are some notable examples of certificated aircraft where a rigorous process didn’t uncover a particular fault until years or decades later. Is that evidence of negligence?

I’ve had the honor of meeting with Dick VanGrunsven and you won’t find anyone more concerned about design, safety, pilot proficiency, judgment, ease of kit assembly, and the use of proven methods. There are thousands of Vans kits flying and he’s become one of the most successful manufacturers in the world.

But building and maintaining an aircraft is still a daunting task. The certificated manufacturers have to regularly defend against a variety of suits—most of which are groundless but very expensive. The “gotcha approach” once a suit is filed doesn’t always serve the industry or buyers of aircraft particularly well. An admission that something could be improved, such as more guidance or improving the hardware, is often used as evidence of wrongdoing when that isn’t usually the case.

This trial will be closely watched from many quarters. In the interim let’s insure that our machines are so well built (if we built them) and maintained that we’re willing to put our families into them. Don’t forget that flying part either.

Bruce Landsberg,
Senior Safety Advisor, Air Safety Institute

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The Watch is over

October 19, 2015 by Bruce Landsberg

4-1Flight Watch is no longer—it was terminated earlier this month.

Officially called En route Flight Advisory Service (EFAS), it was hailed as a great step forward—the ability to get weather anywhere in the country above 5,000 feet agl. It was a big improvement over the standard flight service system when it began in the 1970’s. No longer would one have to listen to some Yahoo (not the browser!) laboriously file a flight plan while an urgent weather update was needed.

Flight Watch specialists had access to real-time radar. By today’s standards—with weather in the cockpit and nearly current radar advisories from ATC—this seems a bit primitive but such is progress. The nationwide frequency of 122.0 worked well. The exception occurred when the high and mighty in Lears and Gulfstreams would foul ten thousand square miles of frequency access to ask how the weather was down in Boca Raton—usually sunny, light winds, and temperatures in the low 80’s. Meanwhile, the bottom dwellers were in a snit to see if the destination was still above minimums, if there was icing ahead, or what nearby boomers were doing.

A few decades back I had a flight to Wichita, Kansas, where a powerful cold front was marching across the country’s midsection. With an IFR flight plan on file, I departed Mt. Vernon, Illinois, in a Cessna T-210 into a darkening midday sky. A hundred miles west lay a wall of convection. It was time to call the “Watch.”

After waiting a few loooong minutes for some non-pertinent conversations to be concluded, St. Louis Flight Watch made it quite clear that this line was nothing to mess with. But there was a hole about 100 miles south of my position that looked flyable. Back on the ATC frequency, I asked for a southerly deviation, which the controller approved.

During active weather it was smart to monitor 122.0. That afternoon ATC and Flight Watch frequencies were an absolute babble; but several minutes later, through it all, the Flight Watch Specialist asked if I was still on the line. Yes…”Well sir, that hole down south has closed up, suggest you reverse course, and it looks better going about 60 miles to the north over St. Louis.” Ok—plenty of fuel and no desire to get bent. ATC again obliged, and it was off to see the Arch. No rain, one moderate jolt, and the front was behind me.

Today we have better options: many more reporting stations thanks to ASOS and AWOS, ATC radars that show where the precipitation is, and the ability to see it all displayed with only a few minutes of delay in the cockpit. 122.0 has become a ghost frequency as the better alternatives have come along. Thanks Flight Watch and to all who spent years helping us along the way!

Perhaps you have a Flight Watch story?

Bruce Landsberg,
Senior Safety Advisor, Air Safety Institute

ASI Online Safety Courses  |  ASI Safety Quiz