JEP FI-2: Take-off, Configuration changes, Landing

(Updated: Flaps discussion.)

(Updated: After giving in last night to exhaustion and a sense of mild frustration at not being able to summarize what I had learned, I slept the night away and was awakened by an epiphany regarding Vx/Vy at 6am; the blanks that existed last night have been filled in.)

(Also, I'm trying out a potential new format for my lesson write-ups; let me know if you like it or have a suggestion that would make it more clear.)

Goals:

• Recognize some airport markings.
• Trim for desired airspeed.
• Familiarize with pattern flight, including take-off and landing.

Flight: I arrived early to preflight and Chuck checked up after me. We discussed what we'd do during this lesson and talked about Vx (best angle of climb, useful to clear obstacles at the end of the runway) and Vy (best rate of climb, most efficient climb and is also the optimal glide speed). Vx on our plane is 67 MPH, so that's when we want to initially lift off the runway on take-off. For the noise abatement procedures that require turning to heading 275 at 400 feet, we stay at Vx until 400 feet then accelerate to Vy (83 MPH), turn off, and climb to the desired altitude. On the way to the end of the runway, we talked about yellow taxiway markings v. white runway markings and that we stop at solid lines because the other side (with the dotted line) is the "hot" side.

The idea was that I'd attempt the take-off, and with a fair amount of weaving as we rolled full-throttle down the runway, the nose lifted up, then the plane lifted up, and we continued to accelerate straight through past 83 MPH because I wasn't managing our pitch very well. Frankly, I was already feeling overwhelmed at that point. Chuck took over for the turn off, then handed it back to me to climb up and head out to the training area up the James.

We reached a straight-and-level flight path, reduced throttle to ~2400 RPM for cruise and trimmed. We used the throttle to climb/descend when trimmed for a certain airspeed; for the plane to maintain a given airspeed when more throttle is applied, it must climb, and the opposite is true for less throttle. Under 2100 RPM requires carb heat, so that required monitoring as well.

We did a few practice patterns (at 1700'). First we trimmed for 95 MPH at pattern altitude (which is 850' for the real pattern). Then came 10 degrees of flaps (note to self: why? descent?). Then more flaps, and throttling back, and pitching down, .... It was a lot to take in at once.

We tried to enter the pattern at a 45 downwind but another plane had just entered downwind and we would have ended up too close behind him, so we did a left 360 for spacing and entered. I followed Chuck's instructions throughout the pattern and got us most of the way in, and he assisted as we came over the runway from a final that started at ~400'. We floated gently before lightly touching down, slowing and turning off. We decided to give it another go in the pattern, so I taxiied us back to 31, we waited for a plane that was slipping his way down to the runway, then I rolled us out there and took off. Better, but not good. We went through the pattern again, with Chuck talking me through it. I didn't realize we were getting blown a little in toward the runway, so we had a very short base and still overshot the runway. My instinct, which Chuck later told me was right, was to correct so that we'd have as straight a final approach as possible, and so that's what I did. We were at 600' this time and so used max flaps, and after throttling back to idle we had a little skip on touchdown but still landed safely and were able to slow in plenty of time to make the taxi turnoff.


Discussion:

1. Why Vx and Vy exist. So Vx is the airspeed that gives the aircraft the best angle of climb; this is useful to know when you've gotta clear an obstacle at take-off. Vy is the airspeed that gives the aircraft its best rate of climb (the most efficient climb); this is useful because, well... the efficiency part is self-evident, and in planning if you know how much ground you're covering given a certain altitude change, then that would be useful.
   
   Anyway, the real thing that struck me is that for take-off you're at full throttle, so that parameter isn't available to help you with airspeed (the focus of the lesson). At take-off, you probably have an idea of how you need to climb out; get out fast or get out steady? Noise abatement at JGG says get out fast to 400' then turn west. How do you get out fast? You shoot for an airspeed of Vx (67 MPH for 388). But that is not a fast airspeed, right? Right, and that's the second part of the point. If the throttle is all the way in, you have to pitch up to maintain that lower airspeed. When you pitch up, you climb. The lower the desired airspeed (for the same power setting), the higher the nose has to be and so the steeper the climb. Thus, maintaining Vx (at full power) requires a climb, which is what you obviously want to do on take-off!
   
   Chuck made a statement regarding Vx and Vy before we hopped in the plane that I understood but of which I didn't recognize the consequences at the time: The plane only knows airspeed. Vx and Vy are about climb characteristics; it can't tell you you're at a 38 degree climb (well, maybe the artificial horizon tells you some things, and the VSI tells you some things, but they weren't part of this lesson so we'll skip them for now). If there's an obstacle and you want to be sure you're doing everything you can to avoid it, you use Vx, knowing that that gives you the steepest climb angle.


2. "Trim for airspeed." This phrase seems misleading (to me) because it suggests (to me) that trim/pitch is the only factor in airspeed when it's not. There are basically three gauges we used: airspeed indicator, tachometer, altimeter. If you want to fly at cruise speed (let's say 120 MPH) at 2000', you get yourself to 2000', set the throttle for cruise (2300-2400 RPM), and then trim to relieve the control pressure that you're having to apply to maintain the pitch/throttle balance.
   
   I wrote that paragraph last night and it both did and didn't make sense to me then. Right now what I think makes sense is that you have to make a choice when you decide to change airspeed. Let's say you're all stabilized and trimmed up for a certain airspeed at a certain altitude and power setting, and you want to slow down. You have a choice: pitch up or reduce throttle. If you change pitch but leave the throttle as is, you'll climb. If you reduce throttle but leave the pitch as is, you'll descend. But of course there's a third choice: do both, and you should be able to maintain altitude.
   
   The real problem with "trim for airspeed" as a phrase is that trimming is the last thing you do and it's optional. You attain an airspeed using the throttle and yoke, and after stabilizing you can then trim to set that airspeed as the plane's new "baseline," like a speed (cruise) control setting in a car.


3. Flaps. The bottom-line statement about flaps is that they don't affect airspeed (UPDATE: This statement is wrong! I'm leaving in the rest of the original discussion because I think the thought process is interesting; I've added a paragraph at the end that puts the truth simply.). I tentatively accept that statement, but haven't entirely worked it through mentally. Flaps are a high-lift device, meaning that they change the characteristics of the wing (camber and chord line) to provide more lift. Full flaps (40 degrees of deployment) seems to me that it would be more like air brakes! If you're in the car with your arm out the window and put your palm vertically into the (relative) wind, the wind applies a lot of force on your hand. If you angle your palm somewhat, you still feel a good deal of force, but the wind also tries to push your hand up. Does this have a corollary for the flaps? The fully extended "barn door" flaps are at an angle to the relative wind, and it seems there would be a fair amount of force against them (drag) as well as increased upwards tendencies (from the wind pushing up and/or the whole Bernoulli/Newton explanation of lift from pressure differential above and below the wing). The lift isn't going to change airspeed; it's not affecting pitch. The drag part of it, though, I'm not sure about. It must not, given the bottom-line statement, but why not? It seems like if it adds to drag, you'd slow down, so you'd need to pitch down to maintain airspeed, and you're using flaps to aid the descent, so that would be a logical thing to do, right?
   
   And then finally, on flaps, if they increase lift, why use them on landing when you want to descend? I presume it's because you also want to bleed off power and idle onto the ground, and since losing power (when all else is constant) results in altitude loss, the flaps control the descent rate. Our second landing was way high, so we used extra flaps.... why? Hmmm... I'm not sure about this business yet.
   
   Update: So the bottom-line statement should have been "We don't use flaps to affect airspeed, even though they do." The flaps do introduce lift and drag in a variable ratio, but they make the plane climb and thus reduce airspeed. In the pattern, we want to maintain airspeed, so we counter the flaps by pitching forward, resulting in descent. Any it may be the case that the descent is too steep, so throttle can be applied to arrest the descent. It's a balance thing.


4. Workload management. In retrospect, it's funny in a very sad and disappointing way that I couldn't come up with 1.3*52 while we were heading back to the airport. I can't even remember at this point what that number means -- 52 is the stall speed in the landing configuration, and 1.3 is a rule of thumb for something (probably the speed to shoot for so you don't stall during approach). I was mental mush by this point in the lesson, though, feeling a little frazzled because I didn't feel that I was getting it quickly enough -- I still needed coaching for configuration changes despite the seeming simplicity of the concepts. Anyway, Chuck asked me to do that calculation. I couldn't. I thought, and thought, and visualized the numbers in my head, and they just laughed at me. Then I got stressed out because I forgot how to multiply! It just got worse. I admitted that I couldn't do it. So he helped me to break it down and come up with the answer. But the real lesson here followed: Simple tasks become monumentally more difficult when you're overloaded, so managing the workload is very important.

Self-Assessment: Overall, I have very little confidence, but it's only the second lesson so that's ok. In the air I can feel the plane and see what's going on and believe that it's just a matter of practice. The take-off and landing part, however, is a touch overwhelming right now because it's new and the margin for error is so much smaller; those parts are kinda necessary, so thus the overall confidence rating of "low."

• Preflight: Good.
• Taxiing: Taxiing was better. Even application of brakes while taxiing needs deliberate work.
• Take-off: Needs lots of deliberate work, but it's too early in the process to pick it apart! Maintaining the centerline while still on the ground under full power (high-speed taxi? :) ) needs deliberate work.
• Maintaining airspeed: Needs practice (different from needs deliberate work; I have a baseline feel for it, just need to employ it more to let it become natural and not an overt thought process).
• Pattern: Needs deliberate work; turning is fine, but managing airspeed and altitude hasn't sunk in yet.
• Radio calls: Decent, will improve with practice.

Next: Tuesday, 9/26 at 4 pm.

• More of the above!
• Stalls
• Maneuvering in slow flight
• Constant airspeed climbs and descents (trim for airspeed and use the throttle, right?!?!)

Hours logged this lesson: 1.5
Hours logged total: 2.5

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