Showing posts with label tachometer. Show all posts
Showing posts with label tachometer. Show all posts

Friday, March 26, 2010

I'll sleep when I'm dead

I'm beginning to realize just how low on the aircraft totem-pole I started. When I began training in a Cessna 172, I knew it wasn't exactly sex on wings. I mean, look:


Doesn't compare to, say, a panty-dropper like the F-35, does it?


Of course not. But all the same, I was thrilled.

Wow
, the five-year-old kid in me hollered, a real airplane! Awesome!

Now that I'm flying a Mooney M20E, which looks like this...


...it's suddenly become apparent what a primitive flying machine the Cessna is. My Cessna 172M has 150 horsepower. That's less than most cars, a lot less. At sea level, it has a top speed of about 140 miles per hour, something any self-respecting Lamborghini would laugh at. To take off, it needs a ground roll of about 835 feet. It climbs at about 645 feet per minute, and has a maximum service ceiling of 13,000 feet.

The Mooney we're flying is a 1961 M20E. (Aircraft age differently than cars do. If you saw somebody with a '61 Chevy, for example, you'd marvel that they managed to keep it running so long. You might even wonder why it's still on the road at all. It doesn't work the same way with airplanes. You just don't fly them until they wear out and then throw them away, like you would a pterodactyl. When a part breaks down, you fix it. And when it gets too run-down to be fixed, you replace it. If an airplane lives long enough, every single part in it will eventually be replaced. Any airplane more than a few years old is a veritable Frankenstein of new and aging components.) Mooneys, as I've mentioned, are sports cars. Even this '61 model has a 200-horsepower, fuel-injected engine. It climbs like a chipmunk on LSD. Our Mooney has retractable landing gear, a fuel pump, a variable-pitch propeller, and cowl flaps (trapdoors which let more air into the engine block during climbs or slow flight).
My Cessna 172 handles like a truck. The thing just putters along through the sky. On descent, it floats down slowly on those big wings, and flares like a goose when landing. It's about as acrobatic as Rosie O'Donnell. It can turn on a dime, as long as that dime is on the ground and you're at least a thousand feet over it.

Our M20E, on the other hand, is what Boss #1 calls "finesseful." It's a finely-tuned piece of machinery, compared to the slab-sided Cessna. Flying it requires a greater degree of control, alertness, presence of mind, skill, and efficiency...which explains why I suck so bad at flying it. You can't pull up too hard when taking off, or the propeller might over-rotate. You really have to have the thing trimmed out properly during descents, or you'll be fighting for proper pitch ("nose authority") all the way to the ground. You'll want to stay below 140 miles per hour, generally, because if you hit any turbulence at that speed, the wings will crack right off.

In the Cessna, I pull the throttle out or push it in, and watch the tachometer needle fall or rise. At cruise speed in the Mooney, I monitor the throttle with something called a manifold pressure gauge. I'm still not exactly clear on what the heck "manifold pressure" is. It sounds like the kind of obscure mathematical principle a physicist would put on a T-shirt. If I have got this correct, the manifold pressure gauge measures the air pressure in the throttle manifold. Theoretically, when you're sitting on the ground with the throttle closed, the manifold pressure readings will mirror actual surface pressure (in inches of mercury). However, at cruise altitude with the throttle open, the pressure will be a lot less, and you can use it to measure throttle settings. Or something like that, I don't know. Perhaps I'm stewed. Perhaps the manifold pressure gauge actually measures how good the pilot is at flying the airplane, which would explain why it's so low all the time.

I do know this, however: for cruise in our Mooney, you'll want the manifold pressure at 20 inches; descents, 15 inches. During Mooney-cruise, you fine-tune the tachometer with the propeller knob.
The variable-pitch propeller, as I so ineptly explained to you, can be adjusted to increase or decrease the blades' angle of attack.

What is the angle of attack, you ask? No, it's not the direction from which you should approach the chicks in the club, wise-ass. And it's not the angle of the Johnson as it enters the coochie, either. Get your mind out of the gutter. This is the angle between the chord line (an imaginary line drawn down from the trailing edge of the wing to the exact center of the curvature of the leading edge) and the oncoming air. Generally speaking, you should keep the angle of attack down to 20 degrees or less. Any more than that and you could stall the airplane. Stalls, if I haven't explained already, occur when the angle of attack is too great to produce lift. If you've been studying the four forces of flight down there at the bottom of this page, you'll know that the force opposing lift is weight. And what happens when you suddenly have 1500 pounds of weight in midair without any visible means of support?


You are correct, Wile E. You fall.

I've practiced stalls several times during my flight lessons, and it's the same sensation as a roller coaster starting down. First there's a buffeting sensation as the air rolls roughly over the wings. Then your stomach flies up into your throat, and you can tell without looking that the plane ain't flyin' no more. Propeller blades have chord lines, too, and an angle of attack. Fixed-pitch propellers can't be adjusted; the air is hitting the blades at the same angle, no matter what. But the blades of variable-pitch propellers can be rotated minutely to change the angle of attack. If managed properly, a variable-pitch propeller makes your plane more aerodynamic and efficient by fine-tuning the RPM, which saves fuel and smooths operation. The gentlest twirl of that knob can send you sailing miles further.

When I flew in a Cessna, I had flying lessons. When I fly in a Mooney, I have flying lessons—on crack. If you want to slow down an airplane, the best method is to raise the nose, and reduce throttle. But my bosses are former fighter pilots. They prefer to yank the airplane into a hard turn, wings pointing straight at heaven and hell, and pull a screaming three-sixty in the middle of the sky. I'm crushed into my seat by two or three G's. My lips and chin go slithering down my neck toward my chest. Shoulders strain to reach my pelvis. My feet are seemingly glued to the floor. Eyeballs bounce off tonsils. I often wonder how my mother (who gets carsick just from reading roadsigns) would react if she were there. The maneuver invariably works. Once we roll out of the turn (eyeballs returning to their accustomed place) we're suddenly 50 mph slower, descending and ready to land.

Adjusting from Cessnas to Mooneys has taken some doing, needless to say.

I still love the 172. It may be slow. It may handle like a truck. It may not be "finesseful." But it's comfortable and forgiving to fly. That's ideal for an idiot novice who prefers not to think too much, you know? My Cessna resembles the placid old Clydesdale that I rode on my grandparents' ranch as a kid. I feel fine just plodding through the sky, floating down on big wings, not worrying about propeller angles or screaming three-sixties.

This week I flew with Boss #1. It was interesting to see Mr. Mooney again. He showed me some spellbinding photographs of his spread up in Montana. It's really coming together. He and his buddy Cowboy are clearing out some willows and putting in a trout pond. The land is surrounded by hundreds of acres of national forest. Elk, trout, flying, all the best of Big Sky Country. I envy him.

We had a good week this week. We earned our pay on Tuesday. There was a possible traffic conflict. Joshua let us know about it first; then I picked up the blip on the TKAS; then Mr. Mooney got a visual. It was a Cessna 182, tracking across our windscreen left to right, right in the path of the climbing UAV. Fortunately it was still a few miles off; we'd had sufficient warning from Joshua. Mr. Mooney radioed the controllers and had them level the UAV off at 7,000 feet, and turn a bit to the left. This they did, and all passed in safety.

Wednesday was warm. We spent the day over at the Victorville airport, and it always seems hotter over there. Perhaps it's all the extra pavement. It was probably in the low 80s, which is just about melting point for me. Or perhaps it was the girls. The FBO at Victorville is called Million Air. It's a swanky flight service which offers plush waiting facilities with leather couches, "quiet rooms" for tired eyes, laundry services, a small theater, free refreshments, weather tracking, and more. And it's staffed by the most attractive assortment of young ladies in corporate skirts and heels, too. Airplanes aren't the only thing they help get up.

I got a lot of work done during our down-time, despite the eye-candy. The second edit of the novel's almost done. Soon it'll be time to send it off to my alpha readers and find out what's wrong with it. I'll keep you posted.

The other noteworthy thing that happened Wednesday was... (Drum roll, please.) ...I got to take off in the Mooney for the first time! I didn't do half bad, either. I did everything Mr. Mooney told me to: push the throttle in slowly and smoothly; raise the nose at 80; don't raise the nose too high after liftoff. I nailed it clean. I flew us out to the rendezvous point and Mr. Mooney took over. He said "good job," which, coming from an old Air Force squadron leader and jet instructor, made my little heart jump for joy.

Thursday was an odd day. We recovered the drone at 12:30 instead of 4:30. Those spring winds were springing up again. But we kept ourselves busy for the rest of the afternoon: it was time for Sierra Hotel's 25-hour inspection. Mr. Mooney had me pull some panels off the engine and battery (a long, painstaking process, involving the removal of about a million screws). We cleaned the engine, checked all the bolts and fastenings for security, the fuselage for dents, the battery for corrosion, the skin for missing rivets, and the engine block for leaking oil. Finding none of the above, we clapped everything back on again and called it a day. I have now officially given an airplane an inspection. I held my head up a little higher as I walked out of the hangar that day. If Jack Ridley had come along at that moment, I could've looked him in the eye and given him a firm handshake.

On Friday we were weather-canceled.
Again. I still haven't worked a full week yet. Mr. Mooney and I finished filling out the daily reports, and then split. I went home and pottered about for a few hours until Mr. Mooney called me down to the airport to give him the key to the hangar. Ha ha, I forgot to leave that with him. Whoopsies.

And now perhaps you're wondering why I titled this post
I'll sleep when I'm dead (instead of sex on wings). That is because I plan, by next week, to have taken my final bartender's exam. Following my passage of this doughty test (a written quiz and a comprehensive speed-trial), I will be briefed on the intricacies of a POS system, and then placed with a job. I intend to work nights and Mondays, around my flying schedule, in order to save up for the


ENORMOUS STUPENDOUS SUPER-COLOSSAL TWO-WEEK TRIP TO ENGLAND I'M TAKING IN JUNE!!!

It's true! Shortly before I left Korea, my English friends Adam and Elaine invited me to Newcastle to watch the 2010 FIFA World Cup from the comfort and chaos of the local pubs. I, having always wanted to watch a football match in an English pub, readily accepted. The main reason I have been striving and sweating to complete my bartender's training, in fact, is so I can get a lucrative job with plentiful tips and save up enough cabbage to actually go. It's looking tight right now, even with two jobs. But I'm going to try it. I don't fancy I'll get much sleep, flying by day and tending bar nights, but it'll be more than worth it.

I'll be in England two weeks. Two glorious weeks of booze, football, travel, castles, parties, and, as the Geordies say, "good craic." Stick around and you'll hear all about it.



Friday, December 4, 2009

Monday: RPMs and magnetos

Do you have any idea how tricky it is to find 29 Palms Airport from the air (even with help from that little purple line on the GPS)? Jeez, they hid that sucker. We were only five miles away from the place when we spotted it, but we did find it, and landed on it. And thus, after three days of cancellations and postponements, Harold and I finally managed to make it to 29 Palms. This marked the second dual cross-country we've done together, and the longest: nearly 100 miles round-trip. I now have barely seven hours of requisite flight-training left, and then I'm through with my private pilot's license. I wanted to spend all four days of Thanksgiving weekend with the fam-bam, so I scheduled my three weekly flying lessons on Monday, Tuesday and Wednesday of Thanksgiving week. Yep, I'd be flying three days in a row: quite a cram session. That didn't bother me. There was some exciting stuff in the offing. On Monday I'd be soloing, but I'd have the reins to myself: nobody would be in the office, even. The book with the key and the required documentation would be left in the plane for me, and I'd simply walk straight through the airport building, climb inside N42126, and go. How cool is that? Tuesday and Wednesday would be given over to cross-country. On Tuesday, Harold and I planned to fly to 29 Palms, a town of some size and scenery west of here (near an also-sizable Marine base). On Wednesday, I'd solo to 29 Palms and back. It didn't fall out like that, though. Heck, no. Let's start with Monday. I got to the airport, duly bypassed the flight school office, and sauntered right out to the plane. I leisurely performed my preflight inspection, a self-satisfied grin on my face as I planned the takeoffs and landings I'd practice and the maneuvers I'd pull over Bear Valley Road. I climbed in and started the plane, not without some difficulty. It's been getting down below freezing at night lately and when it's cold, the engine gets cranky (no pun intended). So I primed the bejesus out of it and finally fired 'er up. Everything was proceeding normally until I taxied down to the run-up area for runway one-eight. As soon as I tried to throttle the oldLycoming engine up to 1700 RPM for my run-up, something weird happened. Dumbo swooped down out of the sky, opened the door of the plane, and handed me a complimentary in-flight bag of peanuts. No, no, I'm just kidding. That would've been really cool, though. What actually happened was this: the RPMs started fluctuating rather severely. Instead of smoothly accelerating up to 1700 (from 1000) the tachometer needle jumped and jerked and stopped and started. The engine's smooth roar suddenly tripped and staggered. I powered down quickly, then cautiously powered up again. The same thing happened. The third time, the power succeeded in reaching 1700 RPM, but it wouldn't stay there. The needle wobbled back and forth, as did the pitch of the engine noise. Not good. Well, I didn't want to muck with it if there was something screwy preventing the pistons from revving smoothly. I didn't want to be caught in mid-air with my pants down. Not in an airplane, anyway. So I taxied back to the ramp and, lo and behold, there was Harold. He'd just dropped in to the airport for a few minutes with his eldest son before driving all the way down to Oceanside to pick up (heh heh, didn't I think this was appropriate under the circumstances) a new engine for N42126. "You just heading out?" Harold asked as I got out of the plane. "No, just coming back, actually," I answered as I unfolded myself. I proceeded to explain the trouble. Harold, puzzled, got in and (with me standing over the right seat, with the door open), proceeded to fire up the engine. Before I tell you how that went, let me share a few choice words about what it's like to be standing anywhere near a propeller aircraft when it's going full blast. You know how when you're riding in a car you're completely oblivious to the amount of air that's moving past just inches away from you? That invisible element, howling along at ridiculous speeds, casually and undetectably deflected by the windshield? Well, now picture yourself standing under the wing of a Cessna 172, only your head and shoulders inside, the door open, directly behind the propeller whirring at full speed, the engine roaring, the wind screaming past you. I felt like I was going to get caught with my pants down after all, because the wind was about to tear 'em off. There was absolutely nothing wrong that Harold could detect. It seems that in between the run-up area and the ramp the mysterious engine ailment had melted away. Perhaps literally: Harold figured Imight've had a little ice in the carburetor. The run-up had probably melted it (or me turning on the carb heat halfway down the taxiway and therefore negating the reason for returning to the ramp in the first place). Harold believed me, and I know he didn't hold it against me or think me silly or overcautious. He's a good man and a good instructor. Plus he knows that, in the world of flying machines, there's really no such thing as overcautious. (My old flight instructor Mike used to tell me, "There are old pilots, and there are bold pilots, but there are no old, bold pilots.") But I felt pretty stupid regardless. Anybody's bound to feel frustrated when they perceive a problem (say, a hideous monster lurking just outside the window) and then when everybody turns to look, the problem has vanished. Makes you doubt yourself. Anyway, not to be thwarted by some minor technical difficulties, I jumped back in the plane and taxied back to the run-up area for the second attempt. No soap. This time it wasn't the RPMs, it was the right magneto. During run-ups, it's customary to check the magnetos and make sure they're both working properly by turning them off one at a time and seeing if the other still runs. You do this by flipping the key in the ignition switch to "L" (leaving the left magneto on, and turning the right off), then back to "BOTH"; then flipping it to "R" (leaving the right on, and turning the left off) and back to "BOTH." As you do this, you observe the tachometer and make sure that the RPMs don't drop by more than, say, 250 (when one of the magnetos is off). Well, darn. That morning, whenever I turned the key to "L," the tachometer needle would fall like an egg from a tall chicken. I had to flip that switch back to "BOTH" but quick; the RPMs were falling off so fast I was afraid the engine would just die right there. I repeated the test three more times, with the same result each time. The hell with it, I finally decided. Flying like this wouldn't be advisable, or safe, or sane. Normally I'm the first guy to try something inadvisable, unsafe, or nuckin' futs, but I didn't feel like it this morning. Particularly not in a rented airplane. So I taxied back to the ramp (Harold had departed in the meantime), shut down, secured the plane, and stomped back to my car. I left a note in the cockpit explaining the trouble, and drove back home. That was Monday's flight lesson.