October 7, 2017
OK I was off to Vermont on a business trip where a bunch of things would go wrong with the trip and here they are.
Each of them is a learning experience, and N844X continues to deliver amazing utility with ongoing lessons along the way.
This was from Columbia SC up to Burlington Vermont non-stop, so starting with full tanks of fuel was the name of the game.
WRONG-THING 1: Not enough fuel cause the fuel drains from the outer bays to the inner bays slow.
I had ordered the tanks topped off and the line-man had indeed topped off each tank and then driven away.
It sure SOUNDS innocent, doesn’t it?
But here’s the thing: To prevent sloshing of fuel in the airplane, the wings, which are ENTIRELY full of fuel from the root all the way out to the tips (with the exception of space for the landing gear and flaps), is divided by ribs with holes to let fuel flow from the outboard bays where the fuel goes into the inboard bays where the fuel is drawn rather SLOWLY. This means that if the lineman simply pumps fuel to fill the outer tank and leaves, fuel flows from the outer tank down into the inner tanks over the next few minutes, leaving the fuel tanks not ACTUALLY all full!!!! That is exactly what happened here, and a check of the fuel level showed that it was down about an inch from the top. An inch from the top. How close is that? Is that close enough to call it a full tank? Should I just call it good enough and fly? How much fuel were we really missing here? Can you guess? I couldn’t.
So I called the fuel guy back out and had him REEEAAAALLLLLY top of the tanks to the top, now that the fuel had drained from the outboard bays down to the inboard bays, and 844X took (drum roll please) an additional SIXTEEN GALLONS! EIGHT gallons per side!! My economy cruise is 32 gallons per hour, so that 16 gallons was a whopping THIRTY MINUTES of flight time. That’s a LOT. OK I put eh fuel caps back on after FULL fueling, noting the right fuel cap felty a little LOOSE somehow… oh well no big deal it has never been a problem before. Ok fueled up it was on to the next problem that taught me more about the airplane… read on….
WRONG-THING 2: Maintenance ran the battery down.
Ok now with FULL fuel it was time to start the engine. Now here is how the PT6 works: The combustion temperature in the engine is so high that it will literally MELT the engine case if the combustion ever comes into contact with the case. The fuel burns at well over 2,000 degrees F.. far hotter than the melting point of aluminum, of which the engine case is made. The only reason the engine does not melt itself into a puddle of molten aluminum on the ramp every single flight is that an insulating current of AIR flows BETWEEN the combustion and the engine walls, insulating the engine from its’ own combustion. But here is the trick: The turbine must be spinning at good clip to move enough air through the engine to keep that insulating blanket of air in place! Too little turbine engine RPM? Melted engine. So, when is the engine going to be the HOTTEST? When the turbine is the slowest, of course, giving the most tenuous layer of insulating air. When is the turbine slowest? During starting, of course, when the weak little starter is all that you have to spin the turbine… not the torrential rush of air resulting from the output of a mighty 850 horsepower. So, the engine is hottest when the turbine is slowest, which is at engine-START. A well-charged battery is the key to getting enough juice to the tarter to get the cushion of air flowing through that engine at start. Now, the shop had been working on the air-conditioning system.. had they run my battery down? I hit the starter and heard the weakest, quietest sound I had ever heard from the starter. Yup, the battery was low. The starter dragged up to 13.0% Ng, the absolute minimum at which you are supposed to introduce fuel. Well, it’s within limits so I engaged the fuel. The turbine sluggishly came up to speed as the fuel started to burn and build the air-insulator. I HELD the starter button down to help, as the temperature went up, and up, and up.. up past the max-continuous temperature of 800 deg C (normal for every start) and up to the max-start temp of 1,000 deg C. And getting closer, and closer, and closer, peaking with in FIVE DEGREES of the maximum allowable start temperate of 1,000 deg C before falling back down as the turbine sped up to normal idle.
They say that 13% Ng is the minimum-allowable Ng to introduce fuel to stay within the 1,000 deg C start temperature, and it turns out that for a fall day in South Carolina with a cold engine doing the first start of the day, they mean it! IF the engine had been hot from a previous run, or if it had been a hot summer day, the temperature would have been over 1,000 deg for sure! SO, if you ever see only 13% Ng, the minimum allowable for start, then watch out: You can only really use that to start the engine if it is cold, on middling-temperature day. Hot engine or hot day? DON’T PUSH IT. I was as close to the limit as you can get and only having a cold engine on a middling 70-degree day kept me under the start-temp limit.
Also if the shop runs your batteries down playing the air conditioning: GET A GROUND POWER UNIT to start.
WRONG-THING 3: Fuel all over the place!!!
OK taxiing out with the ITT nice and cool with a perfectly-tuned idle fuel flow and turbine RPM, and absolutely-full fuel tanks, it was blast-off to the wild blue yonder with the usual steep climb that comes with a carbon-fiber bird that weighs only 2,611 pounds and has 850 hp. Climbing up I noticed something in my lateral peripheral vision: FUEL LEAK! Fuel was STREAMING from the right wing fuel-cap in a white torrent, forming a streaming trail behind the airplane, with fuel circulating back onto the aileron in the turbulent flow that exists on the aft portion of all wings. BUT THE FUEL CAP WAS IN PLACE! But fuel was GUSHING out from underneath it somehow, all over the wing and aileron and into a healthy stream behind the airplane. I immediately stopped my climb and leveled the airplane as I turned back to the airport. As soon as I leveled the plane, the stream of fuel instantly stopped. It all became obvious in an eye-blink: The fuel cap was JUST loose enough to let fuel leak out of it when the nose was pointed up at the sky, the fuel level literally SUBMERGING the fuel cap in jet fuel, so that any possible gap would be exploited. As soon as I lowered the nose to level, the same attitude where the airplane was fueled, the cap was not literally submerged in jet fuel so no leak occurred. Dang. I guess that loose cap should have gotten a little more attention, eh? I made an immediate precautionary landing, taxied right back to the ramp (NEVER FORGET YOUR LANDING GEAR IN CASES LIKE THIS WHERE YOU GET DISTRACTED!) and had my trusty little tool-kit out before the prop even stopped turning. The fuel caps have little nuts on the bottom that you can adjust so easy it is ridiculous to get the fuel caps to be as loose or tight as you like. A half-turn and the fuel cap was nice and snug! A re-top-off of the right tank and it was off to the deep blue again with no further issues!
RIGHT/WRONG THING SUMMARY: N844X
N844X runs South Carolina to Vermont in two and a half hours. To say that this first de-pantses the airlines and then gives them an atomic wedgie is rather an understatement on many levels. The utility and fun and empowerment of the airplane is simply stunning. With over a 1,000 nm range, it can go far, at 300 knots, it can go quickly, and with a 77-knot short-field approach speed, it can get into most any airport. If the utility of an airplane is measured by how MANY airports it can access, multiplied by how FAST it can access them, I do not think that there is any airplane in the world that can touch the turbine Lancair Evolution.
BUT: It won’t JUST carry you around. You don’t get off that easy. You have to be willing to constantly learn all of the lessons that it has to teach you.
In this ONE SINGLE DEPARTURE, keep your tanks full with a re-check, your batteries charged with a GPU after maintenance, and your fuel caps adjusted for solid snugness if you are topping off and climbing steep.