Category Archives: aviation

It’s getting close!

To get a pilot’s license or rating in the US, you have to pass a practical examination with an FAA examiner.

Side note: “What’s the difference between a license and a rating?” you ask. A license gives you flying privileges for a particular category and class, such as  “airplane, single-engine, land” or “Zeppelin.” A rating gives you additional privileges for whatever licenses you hold, such as an instrument rating (which you use in conjunction with a single- or multi-engine airplane license, a helicopter license, or whatever.) 

The examiner may be an FAA employee, but more often is what the FAA calls a DPE: a designated pilot examiner. Think of the DPE like a sort of super-instructor: a civilian instructor who handles practical exams for the FAA and has the power to grant, or deny, your license based on your exam performance. Each FAA field office has a list of DPEs to which it has delegated this authority (here’s the San Jose list.) 

How do you know what the examiner will test you on? There’s a document for each license and rating known as the Practical Test Standard, or PTS,  that tells you. For example, the parachute rigger PTS spells out exactly what a parachute rigger must know; likewise the PTS for various pilot licenses.  The PTS I’m working on is here; it sets out three things:

• What the examiner may and must test the applicant on during the oral exam. Most of these descriptions are very broad, and include the phrase “exhibit knowledge.” The DPE can ask you pretty much anything as a means of seeing whether you can exhibit knowledge; there’s no category of things they cannot ask you.
•  What maneuvers the examiner may and must test. Most of these are self-evident: climbs, turns, descents, straight-and-level flight, steep turns, and so on. In a few cases, the examiner can choose one (or more) maneuvers from a list. 
• What performance standards each maneuver requires. For example, a steep turn requires 45° of bank, ±5º, and you must maintain altitude ±100 feet.

As you might imagine, the practical examination is a big deal. Before you can take it, your CFI has to give you a logbook endorsement indicating that you’re ready. This endorsement means that your instructor thinks you’re prepared for both parts of the check ride: the oral exam and the practical flight test. Preparation is super important. I’ve been studying the PTS so I know the required precision for the maneuvers, practicing the maneuvers both with my instructor and solo, studying the ASA check ride exam prep guide, and watching the King Schools check ride prep course. Of these things, the most important is the flying practice. The two things I need to nail down are crosswind takeoffs and landings and short-field landings; more on those in the next post.

There’s an old saw in aviation: to be a successful pilot, all you have to do is make sure that your lifetime total of takeoffs and landings match. With that in mind, student pilots spend a fair amount of time practicing various kinds of takeoffs and landings to become proficient. In this particular session, we worked on soft-field takeoffs and landings.

One thing that many non-pilots assume is that airplanes can take off or land pretty much anywhere. This is true for some values of “airplanes” and “pretty much anywhere.”  It’s true that almost any reasonably level surface of sufficient length can be used as a landing strip, but some airplanes are much better suited to what we call unimproved strips– those that aren’t paved– than others.  If you watch almost any TV show involving Alaska, for example, you’ll see lots of video of airplanes landing on grass strips, dirt, gravel or sandbars in rivers, snow, and ice. Some of these airplanes will have tricycle gear (meaning a nose wheel and two main gear located under the fuselage), while others will be taildraggers (which use a steerable wheel under the tail, along with two main gear). Some will have skis, while others will have big bush tires. But what about your everyday, run-of-the-mill Cessna or Piper? It turns out that they can operate just fine from many kinds of unimproved runway, including grass and dirt strips. More to the point, though, in case of a precautionary or forced landing, it’s really important to know how to take off and land safely on soft-surfaced runways, so we practice it.

For a soft-field takeoff or landing in a tricycle-gear airplane, one key is to try to keep the nose wheel off the ground as much as possible by keeping the yoke back. As airspeed increases, keeping the yoke back raises the nose, lessening the load on the nose wheel and reducing the chance that it will dig in to the surface and flip the plane over. As you land, keeping the yoke back allows you to convert forward airspeed into lift, which has the beneficial effect of slowing the airplane down quickly without using brakes and while keeping the nose wheel out of the mud, or whatever is on the surface.

To accomplish a good soft-field takeoff, there are a few other things to do. First, momentum is your friend. Once you begin to turn onto the runway, you don’t stop to line up (provided, of course, that ATC hasn’t told you to “line up and wait,” which means that they’ve cleared you to line up on the departure end of the runway and wait for clearance to actually take off while another aircraft lands), and you control your taxi speed such that you don’t have to use the brakes as you turn to align with the runway. As you’re completing your turn, you advance the power smoothly to takeoff power while keeping the yoke back. Once you gain sufficient speed to take off, you add enough up-elevator to leave the runway surface and then immediately push forward so that you don’t climb.

“Wait, what?” I can hear you asking.

Flying machines can benefit from something known as ground effect. This is what makes hovercraft work; an airfoil moving within a certain distance off the ground will generate a sort of cushion of air that provides additional lift and reduced drag, beyond what the airfoil generates on its own. You might remember from a previous discussion that every airplane has a characteristic speed at which it climbs best— it gains the most altitude for each foot of forward motion at that speed. The goal of keeping the aircraft in ground effect is to keep it off the muddy/sticky/grassy surface– which would just slow it down– and allow it to accelerate to best-climb speed as quickly as possible, while surfing the cushion of ground-effect air. This takes some getting used to because your learned reaction to leaving the ground is to put in enough pitch to climb at the desired speed. Instead of doing that, you have to force the aircraft to stay close to the ground until it’s time to climb. This is easy to do; it just requires some extra thought. Once you’ve reached best-climb speed, you can trim the aircraft to maintain that speed, retract the flaps (if you added any), and transition to a normal climb.

Soft-field landings are all about speed. If you’re landing on a soft field it’s a good bet that the field is also shorter than you might like, so you’ll want to slow down your approach. Even if the field is long, though, you’ll still carry 5-10 knots less speed into the approach. For short-field approaches in the 172, I fly 70 knots with the first 10° of flaps, then I slow to 65 knots with 20° flaps and 60 knots with full flaps. If you do it right, you’ll end up in your landing flare doing no more than about 40 knots. Think of what this means in practical terms: if you’re landing on a plowed field (let’s say) because of an engine failure, if you can cut your touchdown speed by 20 knots, you’ve reduced the kinetic energy you’re carrying by a large amount, given that kinetic energy changes as the square of velocity (remember good ol’ KE = 1/2mv^2!)

Short-field takeoffs and landings are different beasts; here the goal is to take off or land within the minimum distance possible, perhaps including clearing an obstacle on the approach or departure. For example, the airfield at Milton, Florida (2R4) is a great place to practice short-field work because there are trees several hundred feet from each end of the runway. These don’t present any real danger, but they make a great target; in a short-field approach, you fly a steeper than usual descent to clear any obstacles, then land a bit firmer than usual– your goal is to avoid any unnecessary float, because float translates to additional distance flown down the runway. You may not have any additional distance to spare. Because it’s late, and I’m sleepy, rather than go on about short-field work I’ll leave this AOPA Flight Training article for those who are interested; it’s pretty good.

[ This is the first of a series of flight blog entries; each one will both cover what I did in a specific flight and try to explain what it means. It’s as much a review tool for me as a means of sharing my enthusiasm about aviation; feel free to leave questions in the comments…]

Tuesday morning I was scheduled to fly a cross-country flight with Andy. As with so many other things, “cross-country” means something completely different to normal people than it does to pilots. The FAA defines cross-country time in part 61 of the Federal Aviation Regulations (FARs). The magic distance in this case: 50 nm (that’s “nautical miles,” as opposed to “statute miles”, which normal people use for highway distances and so on.) In order for a flight to count as a cross-country flight towards your private pilot license, you need to fly at least 50 nm from the point of origin and land at an airport.

I planned a route from Palo Alto, whose airport identifier is KPAO. The “K” means it’s an airport in the US. Canadian airports are tagged with C, Mexican airports with X, and so on. This identifier, interestingly, is the same as is used for radio station call letters– go figure. Anyway. my route was from KPAO to the small airport in Columbia, Caifornia; its airport identifier is O22. (No K. Why? It’s a small, non-towered airport, and their identifiers don’t get the national prefix. Other examples include E16 down in Gilroy and 1M3 near Ardmore, Alabama.) The route would take us from Palo Alto to Columbia, then back to Tracy (KTCY), then back to Palo Alto. Here’s what it looks like:

Andy wanted me to plan on using two radio navigation aids– known as VHF omni-range stations, or VORs. You can see ten in the upper right of the map above– they’re circles with a compass rose surrounding them. Lots more on VORs in a future installment…

What does it mean to plan a cross-country flight? Well, the FAA has a useful answer. Section 91.103 of the FARs has this to say:

Each pilot in command shall, before beginning a flight, become familiar with all available information concerning that flight.

“All available information” explicitly includes data about weather, runways, takeoff and landing distances (which are influenced by terrain, weather, aircraft loading, and runway conditions), and anything else that you need to know to conduct the flight safely. In the case of this flight, that meant getting a weather forecast (a subject for a future acronym-filled post), reviewing the airport data for Tracy, Columbia, and Palo Alto, plotting a course using landmarks for dead reckoning, and calculating estimated time and fuel usage for each leg of the flight. There are electronic tools that can automate flight planning, but I didn’t use any of them; I did it the old-fashioned way, using a chart, a pencil, and a Jeppsen navigation log like the one shown below. (OK, I did cheat; I used an Excel version of the nav log.)

Tuesday morning dawned clear and cool; when I got to the airport, there was a scattered overcast near the airport but it was clear to the east, where we were going, so off we went. During the preflight, I’d programmed the G1000 with the planned route of flight so that it could give me steering cues… as long as it was working, that is. We took off to the north, made a right turn at the west end of the Dumbarton bridge (because that’s the standard departure procedure for this airport– if everyone taking off goes to the end of the auto bridge, and all the incoming traffic flies to the parallel train bridge nearby, it’s easier to keep the streams separate.) Winds were fairly light. The G1000 has a nifty display that shows you the winds aloft, which is good because the winds aloft forecast was wildly off. 

One important thing I learned: how to correctly adjust the air/fuel mixture at altitude. This is too complicated for me to explain here, but basically if you adjust the mixture adjusted properly you’ll get the optimum balance between engine temperature (too high or too low are both bad) and fuel consumption. The G1000 makes this pretty easy; it has a separate mode for leaning, so you bring that up and start tweaking the mixture until you hit the desired temperature. Anyway, this was a fairly new procedure for me. 

I had no problem flying to first the Manteca VOR and then the Linden VOR. All the while I was keeping track of our position on my paper chart too, which was useful because Andy simulated a failure of the GPS moving map display so that I had to rely on my primary VORs and charting to figure out where we were. My first problem came when we were about 10 miles away from Columbia and I needed to spot it… and couldn’t. Take a look at this picture to see why (the full-size version is better):

See that yellow line: that marks the distance I was from the airport. At my altitude of 3500′ it was nearly impossible to see if you didn’t already know where it was. Which I didn’t. Luckily I’d noted that I needed to call Columbia’s traffic radio at 5nm west of the reservoir, so when I saw the reservoir I knew I was in the right general area. Andy had to point out the airport location, though he later told me that one of the reasons he sends students to that airport is because it’s hard to find.

Another thing about Columbia: there are hills all around it. The field itself is about 2100′ above sea level, which means the altitude at which you fly traffic patterns there is about 3100′. That still seems kinda low with the hills about; it is deceptively difficult to accurately judge your altitude above forested, crenellated landscape. I made a decent landing despite that, then we taxied back and took off again to Tracy, or so I thought.

I still didn’t have a working GPS, but thanks to my nav log I had navigational references, courses, and so on to help figure out where I was going so that wasn’t a big deal. There is very little to see in that part of the world, too– if you try hard you can see Copperopolis but that’s about it. On the way, Andy decided it would be fun for me to have a simulated emergency so he pulled the engine power to idle and said, rather cheerfully, “You’ve just had an engine failure.” Then he sat back and watched.

There’s a procedure for this, of course, in which I’ve been well drilled. First thing: fly the airplane. Every airplane has a characteristic speed known as V_y. This is the best glide speed; in a Cessna 172, V_y is 68 knots, and you’ll get about 9 feet of forward flight for every foot of altitude you lose if you maintain that speed. If you go faster or slower, you don’t get as much glide.

Step 2 was to figure out where to go. A little knob-twisting on the G1000 revealed that Oakdale was the nearest airport– about 7 nm away. Andy quizzed me to see if I thought we could make it; at 4000 feet, if I maintained V_y then we should be able to glide about 36000 ft, or close to 7nm. So that’s what I did. Meanwhile, step 3 was to run through the checklist for a failed engine, including checking the fuel tank selector, making sure the fuel cutoff valve wasn’t engaged, simulating a Mayday call, and– oh yeah– doing all this while maintaining the right speed and calling Oakdale traffic to let them know we were on the way in.

I arrived at the arrival end of the runway a little higher than I would have liked; Andy converted my approach by extending our downwind leg and landing in the opposite direction. I made another good landing, then we discussed the importance of flaps, which I hadn’t used enough of. More flaps would have increased my descent rate enough so that I wouldn’t have been too high on the approach end. We took off again and flew back to Palo Alto without any further emergencies or tomfoolery, then I made another good landing and put the airplane away.

Key things I learned during this lesson:

• If you have a thorough nav plan, then losing your GPS is no big deal. Even if I had lost my VORs I could have navigated to Columbia and back to Palo Alto (though in that case I’d’ve stayed at Columbia until the airplane got fixed; in this plane, the avionics are all integrated and anything that would kill GPS and the VORs would make it unairworthy until repaired.)
• V_y is critically important. There’s an old chestnut: “speed is life, but altitude is life insurance.” Very, very true.
• I have a hard time judging my approach heights at airports in hills. This is just something I’ll have to get used to.
• I need to get better about remembering to use my flaps during emergency landings. They’re part of the flow check, and my tendency is to check them off and then not return to put them down later when I need them.

Technorati Tags: lesson, flying

Just because I can, let’s make this one an all-aviation edition!

• I cannot. Even. IMAGINE. doing what this guy did: ejecting from a crippled fighter over a thunderstorm and then descending through it by parachute. Learned a new vocabulary phrase, though: cloud suck.
• This superb post is about aviation all right, but it’s really more about life. Wonderfully written and quite moving.
• There’s a lot of debate in the military aviation world about whether the Marine Corps can afford to buy the F-35B. Here’s an example.
• Ever hear of the Corn Field Bomber? Surprising story of what happened to an aircraft whose pilot had to eject.
• Alexandria International is a fine airport, sources say. I’d have to agree.
• Apparently there’s a book called Abandoned and Little-Known Airfields. Actually, that sounds rather fascinating.
• James Fallows frequently writes about aviation, and, when he does, it’s always worth reading. I didn’t even hear of the I-287 crash until I read his post about it.

Merry Christmas!