Slipping an RV-6A on final

[DaAV8R]

Originally Posted by Bob Axsom

Returning non-stop to Fayetteville, Arkansas from the race in Waupaca, Wisconsin (northwest of Oshkosh) with standard 38 gallons capacity. I have a new EI fuel flow gauge and EI fuel quantity gages (that Jeanine and I calibrated when we built the plane). That new gauge is worth its weight in gold. It was a bad weekend weather wise but we finally got the race in on Sunday, after the folks in Waupaca got home from church, starting at about 12:30 local time (CDT). I landed back at Waupaca after the race and refueled to start the trip home from PCZ to FYV. I felt there was a chance I could make it all the way so I took the direct route which I knew contained no restricted areas and no TFRs.

Scattered to broken clouds were starting to come back in at 3,000 but it was clear beneath them (it was low ceiling and visibility for the three days I had been there before Sunday). I took off and set my course at 210 magnetic direct on TruTrak and Altrac engaged at 2,500 ft. The trip became overcast with light rain and at one point I was forced down to 800 ft AGL to stay below the clouds but nothing worse than that. South of Mexico, Missouri things improved greatly but I was limited to 4,500 MSL. The Springfield Class C air space caused a problem because the top was right there at the cloud base. I contemplated calling them and asking for a transition directly through the center but my independent nature resisted that so I set a course for Neosho, Missouri knowing they had self service fuel and the price is supposed to be good.

When I cleared the outer ring I shot a trial flight plan direct to FYV and determined that it was just within the range of the tank I was using based on the 9.3 GPH burn rate and I had 4 gallons in the other tank still. I decided to proceed direct to FYV clear of the Class C. The tank I was on dropped to 3 gallons in route and then 0 with the red light (it is a little bothersome that the last 2 gallons is obscured by this gauge logic but I understand the rationale and thats how it works). I chose not to run it dry which is an option but instead switched to the other tank which still had the green light on and showed 4 gallons on the display. As I cruised down by Rogers and Springdale on the east side the XNA Class C airspace, the yellow warning light came on for the active tank and the display was 3 gallons. Not a problem range wise but FYV sets down in a flat area surrounded by part of the Ozark Mountains and is not visible until you get there. There was no way I was going to give up one inch of my 4,500 MSL at that point.

As luck would have it the winds were light but they were using 34 instead of 16 as I approached from the north.

Two pilots from SkyVenture flight school and a Bonanza called for taxi from the ramp (they use the tower frequency for everything at FYV even though there is a ground frequency). I could see the conflict/complication coming up so I called the tower at 7 miles and closed my communication with the words "minimum fuel" because even though I was sure everything would work out to a satisfactory completion, I could not risk getting into a fuel emergency situation. The tower operator asked if I said minimum fuel and I confirmed the declaration. As I continued on at cruise settings he called back and confirmed my altitude and at that time I saw the airport WAAAY DOWN THERE. He cleared me to land on 16 and I slipped it down to complete my end of the deal with no power required and no anxiety about having to land long or go around at the 1200 ft elevation airport.

It is a tool, that is different from a crab and you have to understand the concept or have a feel for it but you certainly should know how to use it and not be uncomfortable with it in an RV-6.

Bob Axsom

Great write up. It sounds like an unusual arrival with minimum fuel and I assume an extended slip from a fairly high altitude. Do you consider which tank you are using when deciding which direction to slip? I frequently slip my Cessna 120 but have not figured out what combination of fuel quantity and slip duration will un-port the fuel pick-up. I frequently slipped my Bonanza but it had baffled fuel cells so I didn't worry to much about un-porting. Just curious.

[Bob Axsom]

No, I usually bank to the left for visibility but where I was coming from there was no risk of not making it because of unporting a fuel pick up or loss of power. That is always the case in my slipping action which I do to burn off excess altitude. If it is a normal approach from some distance I fly level until I get to the point where I want to get down then I bank over to lose whatever amount of lift I want (like reducing the wingspan) and opposite rudder for directional control until I see what I want then come out of the slip. I never do a long low drag it in approach. I try to get to a point where I can glide in if I lose power then burn off the excess with a slip even when I do a standard left traffic pattern entry. I come in high on downwind and abeam the numbers I roll up on the inboard wing and put in opposite rudder and steep slip around base and final in one continuos curve to rollout, decelerate, flare and land if possible. Traffic sometimes doesn't permit that. Even on a long straight in approach I carry extra altitude and slip it as I approach the runway to set things up for a soft arrival on the approach end of the runway after I have it made.

Bob Axsom

P.S. I think I may have met you when Jeanine and I flew up to visit Kansas City and we tied down at Lee's Summit. We were offered space in the EAA hangar during our stay - but I refused (that's just me). It was very convenient for us to land at the Lee's Summit airport and nearby Kansas City and Truman's Presidential Library in Independence make a fantastic tourist destination. I do not know why but until we did our research and trip planning I had no idea that it was such a fantastic place to visit. The WWI museum and the one art museum that we got to visit (of several there) are exceptional (and yes we had visited the Prado in Madrid and the Louvre in Paris among others). Jeanine was born in St. Louis and I worked and lived there for over 20 years so maybe we were a little prejudiced without knowing it.

Oskosh 2005


B. A.

[Bob Axsom]

Originally Posted by JCSmith

Hey Bob, thanks for the story.
Wow, it sounds like you have a pretty good handle on your aircraft and it's performance. I'm not sure I'm familiar enough yet, with my new plane to be trusting the fuel flow numbers to that extent though. I have been checking the fuel remaining numbers against what I get "sticking the tanks" at the end of each flight and so far, they have been spot on, exactly the same. (Technology is a wonderful thing)
...
Jim

I have a little over 1150 hrs on the airplane and I am the only one that has ever flown it. The EI gauges are very reliable. I know the last 2 gallons in each tank do not show up on the digital displays even though I have ran the tanks dry and verified the the engine gets it all.

I have flown the airplane all over the country in short wing race, mid wing long race and long wing travel configurations since March of 2004 and I do not like to make enroute fuel stops any more than necessary so I established a fuel management schedule 1=0.5 hr; 2=1hr; 1=1hr; 2=0.5hr; 1=0.3; 2=0.3 to empty tanks (main tanks only configuration). This was repeatedly tested on trips, at WOT, 2450 RPM, leaned 100 F ROP EGT Cyl #4. I was not dominated by intense thoughts of fuel economy. Gradually I made mods to get the airplane flying faster until I ran short on ideas. My friends Red Hamilton and Marilyn Boese invited me out to their home in Fort Bragg, CA to put in high compression pistons and approach speed increases from the thrust end of the 4 force picture. It worked but the fuel burn rate increased as well and that is when I became interested in fuel flow because my old fuel management schedule was not usuable anymore. The fuel quantity gauges still performed exactly as they had before so they provide a reliable indication of the current state that is very mature and familiar to me - I know when I am short on fuel for example with a 1 gallon display precision and accuracy above 2 gallons remaining in each tank. I usually try to stay above 4 gallons remaining but the new fuel flow gauge allows me to see how fast I am burning the fuel and cut it back if necessary as well as predict when the tank will be dry in a pinch. When I refueled at FYV after the trip back from Waupaca Sunday the fuel remaining in the airplane was 3.8 gallons and at the 9.3 gallon burn rate that is a 24+ minutes endurance remaining after landing and taxiing to the fuel pump. The engine run/flight time to get back home was 3.9 hours including the idle and taxi time at both airports at a burn rate down in the 1-2 GPH range. 34.2 fuel used means the average burn rate was 8.77 GPH which I am satisfied supports the cruise flight burn rate display. It seems very accurate. I have also found that when I get the engine leaned in the correct range of max power I can use the HP function to find the actual peak power mixture to 1 horsepower precision and actually see the change in ground speed in the GPS directly related to the HP display on the EI fuel flow gauge. Like I said, "worth it's weight in gold" in more ways than one.

Bob Axsom

[walkman]

Originally Posted by Bob Axsom

ISunday the fuel remaining in the airplane was 3.8 gallons and at the 9.3 gallon burn rate that is a 35+ minutes endurance remaining.
Bob Axsom

3.8 / 9.3 * 60 = 24.52

What am I not understanding in your post?

[Bob Axsom]

I whipped out an answer on a calculator long after the flight and I was so happy to see greater than a half hour I ran with it. I'll correct that.

Bob Axsom