Friday, December 16, 2005

Lesson #5 Flying for Range and Endurance

Well, I woke up hoping that yesterday's forecast for this morning was right, and it was. It was a beautiful day for flying, nice and clear, light winds and hardly a cloud in the sky.

I wasn't going to let this "break" in the weather slip by, so when I got to my office I gave my instructor a call and booked a lesson for 11 AM. It's been more than two weeks and I was really looking forward to getting up flying again.

I was a little late in getting to the airport, I found Dave out on the apron filling up the tanks on the aircraft. On our aircraft's key ring there's a key to activate the airport's fuel pump. You put your key into your assigned slot on the panel located beside the pump, turn the key which turns on the pump, then you fill your plane. There’s a fuel register located beside your key that records the amount of fuel your account has pumped. The amount of fuel is also recorded on the pump itself, just like a regular "auto"pump at a service station. This setup allow you and everyone else (with an account) to get fuel whenever it’s needed.

After we finished topping up the tanks, I preflighted the aircraft. I find the preflights getting much quicker now, and I don't seem to be missing anything anymore. When we turned on our radio we noticed that there was alot of static on our headsets. Dave played with the jacks and the radio for a minute or two until he located the problem. It turned out to be the second radio, which I suspect is the original. This radio (which we don't use) must have been turned on by the last person that flew the aircraft. Once Dave turned it off our headsets were clear again.

I finished our run-up and called tower for the airport advisory. I then informed them that we’d be training to the northwest, 4,000 feet and less, back in about an hour, and that I was taxiing us to runway 03.

My forth takeoff wasn't great. Dave as usual was pointing out things on the panel as we accelerated, important things like engine rpm and oil pressure etc. These are things that need to be monitored during takeoff so that the pilot can make a decision in case something doesn't look good. So with me trying to keep one eye on our speed, one hand on the yoke, one hand on the throttle, and trying to pay more attention than usual to the important things that Dave was pointing out to me, I was a little slow in rotating.

This caused us to "drift" a bit prior to actual rotation. It felt like our rear wheels were sliding back and forth a little, as if it we were on ice. They were still in fact on the tarmac, but just barely. This drifting sensation wasn't huge but I did notice it immediately and this made me realize that I should have already rotated. I began to pull back on the yoke just as my instructor started to point this out. The plane wanted to fly and I was keeping it on the ground by not rotating early enough. Another valuable lesson learnt, 65 mph means up.

Climb out was good but our heading drifted to the left again, I was not giving it enough right rudder. I guess I was still a little rattled about my "three wheel runway drifting session" and I wasn't paying enough attention to our heading and the ball.

At this point in time I was less then pleased with my performance, sloppy takeoff and a crappy climbout.... at least I'm getting the radio calls down, that's something I guess. I called tower and told them that we were clearing the zone.

The weather was beautiful and clear over the airport, along the north shore of the island (about 12 miles away) there was a wall of dense cloud hanging over the water. Winds were calm and the warm water combined with cold air created a solid layer of stationary clouds running basically west to east.

We started off the lesson by first reviewing some of the stuff we covered during our last couple of lessons. Dave had me do some medium turns, they went well but I did let the nose come up a couple of times as I leveled out. Next Dave then had me do some straight and level flight at different cruise speeds, no problems here either. I'm starting to get a feel for the plane as I transistion from one power setting to the next.With this stuff out of the way, we started on the new stuff.

First was flight for best range, basically to fly as far a possible per unit of fuel, this is called “vbr” in pilot lingo. In the real world we would calculate our best ground speed base on the current wind speed and direction. Basically you try to fly at an altitude that maximizes a tailwind or minimizes a headwind. You also have to figure in the amount of fuel that your going to burn climbing to this altitude and then determine if it’s worth it, based on the distance to be flown. Aircraft weight and some other stuff also needs to be a factor as well. For today’s lesson we were just going to keep it simple and try to get the most amount of “distance” out of the aircraft based on the airspeed to RPM ratio.

We started off in a fast cruise, then recorded the airspeed. We then reduced our rpms by 100, waited until our airspeed stabilised, trimmed the aircraft for level flight and recorded the airspeed again. We worked our way down until the airspeed took the largest drop, we then went back up to the next highest rpm, this was our best cruise rpm to obtain maximum distance. I then leaned out the mixture until the engine began to get rough and then enriched it just enough to make it smooth again. Vbr was achieved at 2,100 rpm.

The next part of the lesson is flight for best endurance, also call “vbe”. Basically to fly as long as possible per unit of fuel. We started at our best cruise rpm and worked out way down 100 rpm at a time, trimming the aircraft to maintain altitude. We kept going down until we got to a rpm where we could no longer maintain altitude. We then went back up to the previous rpm and this gave us our best endurance. Vbe was achieved at 1,800 rpm.

Dave then wanted to briefly touch on our next lesson, which is going to be slow flight. He wanted to show me what slow flight feels like, and to wrap up today's lesson we'd also do a stall. I was a tad bit apprehensive, as I have never experienced a stall before.

He slowed us down and extended the flaps 20 degrees, then started going over some of the characteristics of slow flight, sluggish controls etc. Then he performed a stall, which turned out to be pretty much a “non event”. He pulled the power back and pointed the plane skywards, the stall warning horn started going off, our airspeed dropped to an indicated 45 mph. I wondered to myself how the heck we were still flying, then the nose dropped on its own and Dave brought the power back up. That was it, all there was too it, no drama, no hundred foot plunges, nothing exciting at all.

We managed to work our way down from the north, away from the stationary bank of clouds to southeast of the airport. It was about time to head back so Dave asked me if I knew where the airport was, I did. I called tower to let them know that we were inbound and then turned us west to take us over our harbor to line us up for a straight in approach for 03.

A few minutes later (on final) I noticed that we were getting a bit low on our glide slope, I mentioned that I was going to add a bit of power to bring us back up, Dave agreed. We were lined up for a straight in approach to runway 03, which took us directly over Charlottetown. This added a bit of excitement, as there were houses and such directly below us all the way down, and we'd also pass over the Ch’town Bypass at about 150 ASL just before touchdown. I’ve driven on the bypass under plenty of planes on final for 03, and I found it pretty cool that this time it was me in a plane doing the flying.

My third landing was much better than my second, with Dave providing assistance as needed.

Another great lesson...

1 Comments:

At 4:28 AM, Blogger Sam said...

Can you provide a reference for the methods you used to determine Vbr? I did it myself and the ratio of airspeed to RPM appears to be linear. I didn't see a definite drop off.

Maybe you could contact your instructor and ask him/her for a source of the information. I would be very interested to see that.

Thanks.

Sam
Murphysboro, IL

 

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