Maneuvering Va

Everywhere I “go,” there’s a lot of talk among student pilots about Maneuvering Speed: what it means, why it’s necessary to know what it is, why it doesn’t appear on the airspeed indicator, and why it reduces in value with reduced weight.

I’ve heard (and read) explanations aplenty utilizing such ideas as angle-of-attack, the increasing or decreasing distance between “flying aoa” and “critical aoa,” wing-loading, designed load-limits, and even manufacturer-imposed limits on elevation travel!

All these have contributed more to confusion than comprehension and I can just imagine what combination of bizarre answers given over the years when asking the student pilot the natural follow-up question (after definition) about why Va reduces with reduced weight. It serves to show, I think, how unnecessarily complicated we make things. No two texts seem to have the same answer beyond the nominal definition of the speed, although they are all correct! The ultimate dilemma (trilemma, quadrilemma?)

Here it is, simple and easy, once and for all:

Maneuvering speed is the stall speed of the aircraft at design load limit and just as with any other stall speed, it is reduced at reduced weight.

This beautiful explanation is courtesy of Rich Stowell’s book—and a few forum posts here and there:

in which he quite effectively tackles all of this in terms of the V-n (or V-g) diagram.

(This post is in honor of my recently departed cat, Cessna. Clear skies and tailwinds, dear girl!)

Hearne, TX

From Bax Seat:

Hearne has one of the finest runways in Texas—7,000 feet of broad, endless white cement. Not hardly any airport, but they have one hell of a runway. It was a “war base” back in 1942. Now it’s a huddle of sungrayed tin buildings and the bleaching bones of two Normandy-invasion Waco gliders. Linda thought they were old house trailers. I explained that those things, full of men, were towed by C-47s and cut loose to glide down in the dark behind enemy lines. Linda looked a long time at the gaunt skeletons, the wind blowing her copper hair. “They were very brave, weren’t they?” And the long-forgotten ghosts lined up on rusted piperack seats grinned and clacked their appreciation.

Gordon Baxter, the good old boy could write!

VORget About It

I can almost guarantee you that everything you know about tracking VORs is wrong or if in the off chance you have become by blood, toil, tears, and sweat, accomplished with VORs, then I can almost guarantee that your system–if it can be called that–is too complicated. But perhaps I’m projecting because it was for me, until I read Never Get Lost by the Austrian author Wilhem Thaller when it all snapped into focus.

I use “read” in a loose sense because Mr. Thaller, bless his German-speaking heart, brutally stuck a knife in the language when he published his book in English. It’s an atrocious translation and almost made me wish I spoke German so I could read it in the original. Since I had neither the inclination or time, I plucked from the book what I could; it made me feel like I was mining for gold in a mound of manure.

With time and Internet wanderings, I found articles on VOR navigation by Andrew Sarangan and Joe Campbell that echoed Thaller and in better English, thank ye God!  Then came Gian Luca Noia on Youtube to translate all that text into full-motion video! If you ever have had problems with interpreting VOR navigation, I promise that this will have you wondering what the big deal was. It will also amaze your instructor(s) when you can tell (within seconds) where you are in relation to a VOR and what’s more, how to navigate with respect to any radial you’re given. Again, instantly:

Flight Tests–A Review

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A review I posted to Amazon.

I knew I was about to read something most definitely not run-of-the-mill when I read the cover that showed the book was endorsed by an organization known as the Live Cowards Club. Since this is a club for which I will handily pass any and all entrance tests, it tickled the old laugh muscles.

Make no assumptions though, this is a very serious book, just written in a humorous manner: that of showing oneself capable of being a good and safe pilot to an examiner. It is mainly written from a South African point of view (so expect to stumble into words spelled weird like ‘manoeuvre’ 😉 ) although the laws of physics holds no matter where you fly. As Davis says, this little book “takes you through each flying exercise and tells you what [the examiner] expects of you.”

Each part of the check ride is examined, from pre-flight inspection to steep turns, to cross-country flying. Each section is filled with tips and the strong voice of a very experienced pilot. In essence, this book will help you get mentally prepared for the test. Here’s one from near the front of the book:

“Try to do everything smoothly. Imagine that you have your 90-year-old granny in the back, and its[sic] her first flight ever. Do everything smoothly, even small things like applying carb-heat, changing power settings or selecting flap. Passengers should not be able to notice changes of power and speed and attitude.”

With equal parts mindset framing, expounding on the philosophy of good airmanship and practical flying technique information, this is a book that punches above its weight class. Five highly recommended stars.

Words Carrying Ideas

I’m not happy to hear that the FAA will be phasing (no pun intended!) out VORs. I’m no Luddite, but VORs have been a most reliable navigation aid for quite a long time. I believe, just as with NDBs, they provide a solid backup that shouldn’t be so easily relegated to the trash heap. GPS is great, really great. I just think throwing our lots in with what’s admittedly an outstanding piece of technology to the exclusion of all the other navigational systems is shortsighted.

I think it comes down to pilots’ aversion to math. Yes, math. The modern aviator doesn’t like angles and “figurin’” preferring the cozy comfort of a magenta line stretching out into the electric distance whispering “follow me.” And so we forget how we got here and how “here” can be passing and perishable. If you think that isn’t true, ask those who have gotten lost because the power to the electrics on the aircraft died or because the batteries ran out. What saddens me is reading stories of pilots declaring emergencies because their GPS receivers had decided to take a well-earned digital holiday.

And so we abandon the tried and true simply because “math is hard.” When figuring out where you are in relation to a beacon becomes too difficult, what hope? However, in the middle of my admittedly hyperbolic, “get off my lawn, you young rascals” rant, I have to recognize something which has bothered me for a long time.

The problem, and it is a very common one, is that the authors of the explanatory texts are unclear. Using sixty words when four will do; tortured sentences; convoluted, flamboyant, overdecorated verbiage (yes, I know …); atrocious grammar. The list of grievances is endless and it makes it so that your average student trying to understand the ideas ends up confused by the words. He cannot see the idea forest for the literary words, if you will bear with the shaky metaphor.

It wasn’t until I branched out and started reading some older navigational material from WWII (check out Google’s library of digitized books) and also some British authors that I started to understand this idea. The older boys used direct sentences that explained in a way sure to provide information while getting out of the idea’s way.

I’ll give an example of this using the explanation of the VOR. I’ll start with the FAA’s description of what a VOR is and how it works, from the Pilot’s Handbook of Aeronautical Knowledge (PHAK):

 

Very High Frequency (VHF) Omnidirectional  Range (VOR)

The VOR system is present in three slightly different navigation aids (NAVAIDs): VOR, VOR/DME, and VORTAC. By itself it is known as a VOR, and it provides magnetic bearing information to and from the station. When DME is also installed with a VOR, the NAVAID is referred  to as a VOR/DME. When military tactical air navigation (TACAN) equipment is installed with a VOR, the NAVAID is known as a VORTAC. DME is always an integral part of a VORTAC. Regardless of the type of NAVAID utilized (VOR,
VOR/DME or VORTAC), the VOR indicator behaves the same. Unless otherwise noted, in this section, VOR, VOR/DME and VORTAC NAVAIDs are all referred to hereafter
as VORs.

The prefix “omni-” means all, and an omnidirectional range is a VHF radio transmitting ground station that projects straight line courses (radials) from the station in all directions. From a top view, it can be visualized as being similar to the spokes from the hub of a wheel. The distance VOR radials are projected depends upon the power output of the transmitter.

The course or radials projected from the station are referenced to magnetic north. Therefore, a radial is defined as a line of magnetic bearing extending outward from the VOR station.  Radials are identified by numbers beginning with 001, which is 1° east of magnetic north, and progress in sequence through all the degrees of a circle until reaching 360. To aid in orientation, a compass rose reference to magnetic north is
superimposed on aeronautical charts at the station location.

H’m. This doesn’t really tell me much about how the VOR works per se and I don’t know how much of that information will be of help to a new student who’s never heard of a VOR before!

The information you get from the FAA’s Flight Navigation Handbook and the Instrument Flying Handbook have close to the same information, a radio transmitting courses from the station in all directions, like the spokes from the hub of a wheel.

But what are its principles of operations without resorting to simplistic explanations like hubs from a wheel? Here’s how brits Bramson and Birch describe it in their 1984 book, Radio Navigation for Pilots:

PURPOSE OF THE EQUIPMENT

To facilitate en-route navigation along selected radials and to provide references for holding and let-down procedures.

PRINCIPLE OF THE AID

VOR is a relatively short range radio navigational aid operating between 108 and 118MHz in the VHF band. It is a pilot interpreted aid comprising an airborne Navigation Receiver capable of being tuned to 100 or more frequencies and a Converter/Indicator which accepts signals from the navigation receiver translating them into simple indications on an instrument face. The airborne equipment is used in conjunction with a system of VOR beacons, most of them situated within the airways network.

To understand the principles of VOR it is necessary to have a superficial knowledge of the radio wave itself.

In the section on electro-magnetic energy the basic wave cycle was described (page 50). In essence the state of the electric current within a cycle (i.e. positive or negative strength) is constantly varying with time. Indeed at any particular time the development of the wave may be identified e.g. half maximum positive rising: maximum negative: zero raising to positive etc. As already explained such a state of development is known as a Phase.

Imagine a radio beacon designed to radiate two beams, one running north and the other running south. And suppose each beam consists of two waves, the north beam emitting its phases in unison and the south beam with its waves at opposite phases (Fig. 41). An electronic device capable of measuring the difference in phase between two radio waves would, in this case be able to tell the operator when he was within the north beam or south beam. In other words the equipment is able to compare the differences between the phases of two simultaneously transmitted waves and since it uses this principle VOR is known as a Phase Comparison aid.

Figure-41

Fig. 41.

THE VOR TRANSMITTER

Using the principle of phase comparison the VOR radiates a Reference Signal in all directions, its phase remaining constant throughout the reception area. A second signal, transmitted as a narrow beam, is arranged to sweep like a lighthouse through 360°. As it sweeps, the phase of the beacon is constantly altering so that its phase comparison with the fixed reference signal will change according to its position relative to the beacon (Fig. 42). In effect a VOR beacon emits an infinite number of beams or Radials through 360°, each possessed of unique differences in phase between the two signals. It therefore follows that with the air of equipment designed to measure or compare the two phases and translate these into headings from the beacons (radials), a pilot would be able to locate his aircraft in relation to the known position of that beacon. The VOR Beacon is adjusted to transmit radials related to Magnetic North.

Figure-42

Fig. 42.

Please tell me which one of the two explanations of the VOR’s principles of operation you found easier to understand?

Now I don’t know if this is a good example in particular of what I’m talking about in general, but if you’re not convinced I’ve got more examples*¹.

*¹ Even though for example is not proof.