I'm constantly amazed that the constants of aviation usually aren't. Many friends, retired airline and military pilots, tell me their experience reflects the same truths. It seems there are a number of popular myths about flying that refuse to die.
One of the most common is that experience is the best teacher. The myth is that aviation is such an unforgiving discipline that you may never live to make the same mistakes twice. While that's true for several of the cardinal sins, it's apparently not applicable for most minor infractions.
I'm living proof. I've made many of the same mistakes two or 10 times, and still somehow managed to walk away. Perhaps best of all, no one else knows about my transgressions.
One thing I've learned, however, is that many of the rules of thumb (and forefinger) we were taught in flight school are simply not true. Or at least, not all the time.
One of the most common misconceptions is that tailwinds should logically cancel comparable headwinds as long as you make round-trip flights and wind direction doesn't change.
Sorry, it doesn't work that way. I'm not sure what the real statistics are, but I'd bet you'll experience headwinds at least 70% of the time. First, a given headwind is more of a disadvantage than an equivalent tailwind is an advantage, because a headwind acts on the airplane longer than a tailwind. Second, even a direct crosswind costs you speed because the aircraft is crabbing partially sideways. Do the math, and you'll find you gain speed from a tailwind in only about the aft 160 degrees, but lose speed from any wind in the forward 200 degrees, obviously not a fair trade.
For flight planning purposes, many of us ignore tailwinds of less than 10 knots and assume we'll break even if we're lucky. The cynics among us also add 20% to any headwind.
We were all taught in flight school that fuel reserves need to be enough for the planned flight plus a 30-minute reserve on VFR day legs, planned flight plus alternate plus 45 minutes for IFR hops.
Even here, there's a, "Yeah, but…" It obviously doesn't make sense to tanker fuel (carry around excessive amounts that you don't need—a heavier airplane flies slower for the same power, so burns more fuel per mile), but make certain you have the fuel you think you have. Pretend the individual tank gauges are inaccurate (because, like airspeed indicators, they often are), and KNOW how much you're starting with.
Under some circumstances, tanks can develop air bubbles that can supplant more fuel than you'd believe. Once in Reykjavik, on a delivery to Europe in a new Malibu, the fuel total didn't look right after refueling for the leg to the UK. I went out to the airplane, popped off both caps, and the level looked to be right to the top. I shook the wing vigorously, the level dropped on both sides, and the truck came back and added 15 more gallons. That's almost an extra hour of range.
As a result of such realities, we also subtract 5% from available fuel, especially when we have four or more tanks aboard. (The more tanks, the more the possible margin for error.) In other words, 300 gallons becomes 285 gallons. That's to allow for any possible overboarding during climb or filling to inconsistent levels.
Most pilots understand not to trust everything they read in flight manuals regarding cruise speed and fuel burn. No, the manufacturers probably aren't lying to you about either figure, but they determine performance and fuel consumption based on absolutely optimum conditions.
There are a number of reasons that manufacturer's specs may not be readily attainable by us mere mortals. First, the flight manual's cruise speeds are derived by company test pilots with thousands of hours in type, aviators who know how to milk every knot of performance from a given airplane. These pilots fly new, well-polished, perfectly rigged aircraft with finely tuned engines, all vents closed, usually operating at max allowable aft CG, in smooth air and ISA conditions. You have about three chances of duplicating those circumstances in the real world: slim, fat and none.
Fuel burn specs are also real but optimized, a result of leaning to the exact EGT in the handbook, often utilizing extremely precise flight test instrumentation that has been calibrated to eliminate any error.
Altimeters introduce a whole new variety of potentially dangerous variations, and not always of their own making. Nearly every altimeter has some error, and pilots only add to the problem.
My most educational experience with an altimeter occurred on a trip to Germany in another Malibu, this one the first Lycoming-powered Mirage in mid-January of 1989. The weather had been bitter cold going into Bangor and Goose Bay, -25 and -40 degrees F, respectively. I had to resort to near-aerobatic maneuvers to get the gear down at both airports after the wheels basically froze up and refused to extend either by the normal, hydraulic method or the emergency system (another story entirely).
Out of Goose Bay, I was determined not to let that happen again. The jet stream was very low and screaming out of the west, providing a spectacular 90-knot push for the crossing to Iceland above 18,000 feet. I leveled at FL210, and soon was speeding toward my destination at just under five nm a minute, admiring the Northern Lights in the middle of the afternoon.
An hour from Reykjavik, I called Iceland control and requested a descent to 1,000 feet over the ocean. The plan was to cruise for an hour in warmer air to make certain the gear would operate as advertised. There were no other idiots out there in the dark of day/night, so Iceland approved my request. I dropped down to 1,000 feet above the ocean, engaged altitude hold and trundled on toward Reykjavik.
After a while, I began to notice a strange luminescence slightly below me, a dim, barely visible, blue-green glow in the solid dark of winter. It took only a few seconds to realize what it probably was.
I stabbed the autopilot disconnect and levered the yoke back as hard as I could, leveled at 2,000 feet indicated, then took a breath, amazed that I was still alive.
I'll never know if Iceland gave me an updated altimeter setting as I dropped through 18,000 feet and I missed it, or if they simply forgot. Either way, it was my fault for not resetting from the 29.92 setting used above 18,000 feet. As it happened, the region was in the middle of a typical Icelandic low, in this case 28.97, almost a full inch below normal. I had been cruising at perhaps 50 feet above the North Atlantic, maybe less, and the shimmering color was the natural illumination of the waves below.
The incident was totally my fault, but the bottom line was I became fanatical about altimeter settings. I update every chance I have. An incorrect altimeter setting is one error I may not be allowed to make again.