Paul's Down-Home Page

I took the boys down to Tuscaloosa last weekend to visit David. The weather was fine, and we had a lovely visit, but it ran a bit long, and then I couldn’t get the plane started. It’s finicky, but it was my fault, not the plane’s. Then I wouldn’t have been able to get back to Redstone before dark, and I’m not night current, so we ended up leaving the plane and driving home (a process made much harder by the fact that it’s impossible to rent a rental car after 6pm in Tuscaloosa on a Sunday). The next day I needed to go back down to pick up the airplane, so I called my instructor to see if he wanted to fly me down there. The flight turned into an instrument training lesson, which was exactly what I was hoping for.

Weather at Redstone on departure was fair: ceilings were about 3500’ with visibility of 4 miles. It started raining just as I was finishing the preflight. John had filed an IFR flight plan direct to Tuscaloosa at 5000’, which turned out to be ideal for getting me some actual instrument time, including flying through rain. This turned out to be a nonissue because when you’re only using your cockpit instruments for navigation, not being able to see because of rain doesn’t pose a probem.

I say “actual” because you can log both simulated instrument time (in which you wear a view-limiting device such as this) or actual time. “Actual” in this context means you’re flying completely on instruments, without visual reference to the ground. In our case, that meant we were flying through a layer of clouds for a total of nearly 50 minutes. That meant that I had to control the airplane’s altitude, attitude, and course using only the instruments in the cockpit. All pilots are required to receive training on this, and to demonstrate proficiency in doing it, as part of the initial training process, but doing it in actual is quite a different matter. It’s very demanding work; you have to keep a consistent scan pattern on your instruments to make sure you’re holding course and altitude.

One key difference is that the best way to do this is to use predetermined engine settings: at a certain RPM and manifold pressure at a given altitude, you can predict how fast the plane will go and to make it climb or descend at a predictable rate, you know how much power to add or remove. Flying on an instrument flight plan often involves reaching very specific altitudes at specific points in space, i.e. you may be told to cross a fix at a given altitude, and you need to figure out how to make that happen.

I did reasonably well; I didn’t have any trouble maintaining my altitude, and my heading control was generally good except for a couple of minor excursions when I got over-focused on altitude or airspeed. You really have to divide your attention between all of the instruments to maintain a consistent flight path, and that’s very much a learned (and perishable) skill.

We made it safely to Tuscaloosa, landed, and I got the Arrow started. I took off first, flying VFR back to Huntsville at 3500’. In the Arrow, I was averaging about 145kts groundspeed on the return, and the flight, which took place between a high layer of solid overcast and a lower layer of broken clouds, was quite nice.

between the layers en route TCL-HSV

After a smooth and uneventful flight, and a decent landing, I logged 0.2 simulated instrument, 0.8 actual, 0.2 VFR for the leg down, plus another 1.0 for the return VFR flight. I’m looking forward to more instrument time… make mine actual!

Sometimes one word can speak volumes. This is especially true when there’s a well-defined and mutually understood vocabulary that all parties in a conversation are using– which is exactly what happens when you talk on the radio with an air traffic controller. Although it often sounds bizarre to outsiders, the back-and-forth between pilot and controller can be incredibly information-rich. The FAA has a standard glossary that pilots and controllers are supposed to use, and you can’t go far wrong by sticking with it. Many of the terms in the glossary compress a great deal of meaning into a few syllables, which is important when you’re busy– which, as either a pilot or controller, you will be!

For example, the controller at a busy training airport such as Palo Alto (which usually has between 500-700 takeoffs/landings per day, a lot for a small airport with a 2500′ runway) could say “One Tango Golf, there’s a 172 on final. If you go right now, then you can take off on runway 31”, or he can say “One Tango Golf, landing traffic, expedite, cleared for take off, 31”. Now consider the workload of a pilot flying into an airport like Atlanta or Dallas, or a controller in the tower cab at Chicago-O’Hare or Newark, and you see why brevity is so important.

My favorite of all these expressions is simple: “unable”. The glossary defines it thus:

Indicates inability to comply with a specific instruction, request, or clearance.

Depending on how you use it, it can mean “I won’t do that” or “I can’t do that.” Rather than provide a long explanation, all you have to say is “unable.” Suppose I’ve filed a route from point A to point B and the controller wants to have me deviate to point C, and I happen to be low on fuel? “Unable.” Want me to turn towards an area of built-up clouds? “Unable.” Because the pilot in command has ultimate responsibility for the safety of flight, as PIC you have unlimited authority to accept, or reject, controller requests or instructions– with the very significant caveat that you may be required to account for doing so. If the controller tells me to sidestep to a parallel runway on approach, and I don’t, and I cause an accident, having said “unable” isn’t going to get me out of trouble.

The magic word works both ways, of course: when you ask a controller for something (“Niner Eight Mike, request lower” to get a lower altitude, for example) the controller can merely say “Unable” and that’s it. Of course, whoever receives the U-word can always ask for something different, or explain why they want whatever it is.

Now I just need to brief the people I talk to most frequently so they know what the word means to. “Dad, can you take me to the mall?” “Unable.”

Recently I had the opportunity to fly down to Louisiana to see my mom, grandmother, and uncles. This was an easy trip: straight-line, it’s 411 miles from airport to airport. It took me 3:12 to get down there and 3:00 to get back. Why the difference? In a word, wind. In the northern hemisphere (and, more particularly, in the US, since that’s where I’m flying), prevailing winds tend to follow predictable patterns: west-to-east for much of the country, and (in general) onshore in coastal areas. The strength and direction of winds aloft vary, of course. For example, the definition of a frontal boundary (the line demarcating where a cold or warm front actually starts or ends) is an area where the wind suddenly changes direction and speed. It’s generally true that you’ll face headwinds when flying from east to west and tailwinds when flying from west to east, but the strength and direction of the winds can change quite a bit as you move across different types of terrain, through different weather systems, and so on.

astute readers can figure out exactly where I was when this picture was taken

In the picture above, the “GS” number in the lower right shows that I had a groundspeed of 148 knots. Since one knot is 1.14 statute miles/hour, that’s just over 170mph. That seems pretty good, considering that it’s more than double the speed limit on any of the roads that link Huntsville and Alexandria (and triple, or more, the speed limit for the West Monroe-Alexandria leg). The 128kts average groundspeed I had going westbound still equates to 147mph. Although a 20-knot difference is nothing to sneeze at, the practical impact is that it saved me… exactly 12 minutes, mostly because the winds kept changing.

That brings up the question of fuel usage. Every powered airplane has a set of performance charts that show you, for a given altitude and power setting, how fast you can go in still air (and remember, airspeed isn’t the same as groundspeed; that’s a topic for another post) and how much fuel you’ll burn while doing so. Book fuel burn for the Cessna 182P is between 12 and 14 gallons per hour, depending on your altitude and power setting. Most rental aircraft are rented “wet”; that is, the hourly rental rate includes gas and oil. In a rental, you therefore have an incentive to configure the engine for best speed even if you burn a couple more gph. When it’s your airplane (or when it’s a “dry” rental) you’re paying for the fuel, so you get to choose: would you rather burn more gph or get there a little later?

The correct answer is “it depends.” Aviation gasoline costs anywhere from $5 to $7/gallon in the US. (Why so much? Why the variance? Those are topics for another post too.) Suppose I can cruise at 130kts for 12gph, or 150kts for 15gph. That extra speed is going to cost me, let’s say, $18/hour. For a 411nm trip, that means I can get there in about 3 hours 9 minutes for just under 38 gallons (so, call it $228). On the other hand, at 150kts I could get there in only 2 hours 44 minutes, but it would cost me 41 gallons of fuel, or $246. In my case, since I was renting a plane, I went pedal to the metal, adjusting the engine for max speed rather than best fuel efficiency.

Now, this is an oversimplification, of course. It ignores the time spent climbing and descending (you burn more fuel in the climb, and less in a descent, but not enough to equal what you burned climbing), it assumes that ATC doesn’t reroute you anyplace inconvenient, and so on; it’s a good enough estimate for our purposes.

Let’s compare, now, the cost/mile of flying versus driving. I drive a 2005 Nissan Altima that gets 30mpg on the highway. Bing Maps says the fastest road route is 514 statute miles. So, that’ll cost me about $60 in gas, as opposed to $384 for the airplane rental. I’m leaving out all the other fixed and variable costs of the car; if I wanted this to be more precise I’d compare the cost of driving a rental car from here to there, but who would do that if they didn’t have to? Anyway, flying is considerably more expensive until you figure the time savings. Bing calls this an 8-hour trip, assuming no stops for fuel, food, or bathroom breaks. I can make it in a hair over 3 in the plane, though I have to take my own food. As with the car, that price stays the same whether I fly solo or with passengers (or cargo, such as the excellent banana pudding I brought back– thanks, Mom!)

Clearly I could come up with a business rationale that values my time at what Dell bills customers for it, or what I bill for it on standalone projects, but the right way to think about it, I think, is that the time I gain is priceless: being able to get to see family and friends, or attend important events, or just get out of town for a trip, is important, and the airplane gives me the flexibility to go farther, faster, more often than I could in a car, for considerably less money (usually) than it would take to fly commercial.

For another time: does it make sense to spend more money to rent or buy a faster airplane? It depends.