# 1:60

0

Mr. Meragers “Letting Down Easy” (September 2007) helped remind me again of that quickly needed and often used relationship in aviation: If you travel one degree on a circle and you travel one mile, the circle has a radius of 60 miles.

In other words, your distance traveled and the distance from the center of the circle has the ratio of 1:60.

Remember how we used this to determine the distance we are from the NDB? Flying abeam the station, we travel one degree and note the time. The time required to fly to the NDB will be 60 times the time required to fly the single degree.

Knowing our airspeed, we can compute distance from the station or, knowing the distance, our airspeed.

This same “magic” ratio applies in descents, too. If you are 6000 feet (one nautical mile) from the airport, and you are 100 feet agl, you will be on a one-degree glide path (1:60). A three-degree flight path would be 300 feet agl at one nautical mile.

This 1:60 relationship comes from converting the 360 degrees around a circle to its distance: 2πr = 360 degrees. Or, r ≈ 360/6.28 (2π, or 2 * 3.14) x one degree ≈ 60, close enough.

Tom Hauch
Charlotte, N.C.To paraphrase Chevy Chases impersonation of then-President Gerald Ford in one of the early episodes of
Saturday Night Live, “I was told there would be no math.”

Of course, some basic aptitude with math is necessary in aviation to avoid things like running out of fuel or overloading an airplane. The more we can do basic calculations like descent rates and time-to-station in our heads-or use prepared tables-the better off well be. Just dont take away my trusty E-6B whizwheel or pull the circuit breaker on my GNS530, please.

IFR In VFR Patterns

Thanks for your article about how IFR and VFR skills complement one another (“IFR Into VMC,” September 2007). Of course, IFR skills and discipline can be useful in a standard traffic pattern, too.

For example, presuming you are a half mile (.5 GPS) on a downwind, it works well to establish a uniform descent rate of about 700 fpm, then turn base and final at 700-750 agl and 400-450 agl, respectively.

Fly all the legs on the correct 90-degree heading and decrease airspeed on each leg (e.g., 80, 70 and 60 KIAS, respectively, in a Skyhawk).

Assuming proper compensation for wind, this puts you pretty much on the 500-foot marker each time. This IFR method greatly reduces the head-turning, key-point estimating and sight-picture work of the VFR landing.

The VFR part boils down to scanning for traffic and making the same adjustments on final that an IFR pilot would make anyway breaking out at 400 agl.

Tom Kramlinger
Orlando, Fla.

So much of flying is a numbers game: How far, how long and, of course, how much? Most things like loading and atmospherics being equal, establishing agreed-upon power and flap settings at certain points around the traffic pattern will always produce airspeeds within a knot or two of whats desired.

Many instructors would prefer a student learn the appropriate power and flap settings, apply them, and keep looking out the window for other traffic while in the pattern.

Missing VNAV “Computer”

I look forward to each issue but now Im doing more reading than flying! Some of your articles should come under the heading of “Things your instructor never taught you…or didnt know.”

However, in the sidebar on page 6 of Septembers issue (“The FAA/NACO VNAV “Computer”), you reproduced a table from FAA/NACO publications providing a “canned” solution to the problem of determining the rate of descent one must maintain at what groundspeed to reach a specific altitude over a given distance.

I cant find it on the FAA/NACO Web site and the two people with whom I spoke thought I was speaking Greek. Got a link? Thanks!

J.A. Krell
Via e-mail

That table is at the front of every printed FAA/NACO instrument approach procedures book. Its also available on the agencys Web site, http://naco.faa.gov/d-tpp/0710/frntmatter.pdf, as an Adobe PDF file. Once you download the file, the table is at the very end.

Confession Is Good

I applaud the “Learning Experiences” author of Octobers contribution, “…doesnt feel right…” for sharing his insightful story of the consequences of continuing an unstabilized approach.

It would have been too easy for this student pilot to blame the whole incident on his instructor but, as it turns out, this story embodies the spirit and intent of “Learning Experiences” in your fine magazine. We all learn from stories like this.

Having said that, I am dismayed a CFI apparently directly contributed to-perhaps even encouraged-what could have been a much more serious event. From the description, it appears this pilots instructor was fixated on the landing aim point to the exclusion of approach speed, among other considerations. When the accident occurred, I presume the pilot was coming in lower than his norm, and raised the nose to maintain a proper descent to the threshold.

Nowhere in the story did the pilot refer to his approach speed and, more importantly, the instructor seemed to think the resulting incipient stall was “looking good” despite the student pilots repeated concerns of the airplane “not feeling right.”

I would encourage this pilot to continue to hone his skills and learn from experiences such as this, hopefully with an instructor that can better teach the fine art of stabilized approaches.

Len Sherman
Via e-mail

VFR Minima

The sidebar discussion, “What Makes Special VFR Special” (October 2007), contains a couple of misleading points. It states, “in most of Class E below 10,000 msl,” you must remain 1000 feet above, 2000 feet horizontally from and 500 feet below clouds, and you need three statute miles visibility. In fact, basic VFR weather minimums are required in all Class E airspace.

The sidebar also observes that, in Class G airspace, you only need one mile visibility and to be clear of clouds to maintain VFR but states, “otherwise, youll need an IFR clearance.”

Of course, you only need an ATC clearance to fly IFR in controlled airspace, which Class G is not.

While it may seem like a questionable idea, it is legal for an IFR-rated pilot in an IFR-equipped airplane to fly in IMC in uncontrolled airspace without filing a flight plan or receiving a clearance.

Jack Yager
Via e-mail

Youre right, of course, and we cant even think of an excuse. But, this is a good time to remind everyone that, if youre having trouble determining your distance from nearby clouds, someone else might be having the same problem in the same airspace.