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Friday, June 1, 2012

Feedback June 2012


LTE versus NETR

I’m not sure what Frank Lombardi is getting at in his Ask the Expert response, "Loss of Tail-Rotor Effectiveness on the Bell 206” (which appeared at www.rotorandwing.com in November 2011): NETR is not LTE, or NRTE should be practically thought of as LTE because one can lead to the other? Or both? In addition, about the LTE concept:

• As it is a syndrome and not a disease in itself since it is describing behaviors that may seem identical if called by the same word, but refers to many different situations and causes,

• As all causes or situations that come under LTE can be overcome by enough tail rotor thrust margin (and obstacles far enough), enough quick pedal reaction, not panicking while applying pedal in the correct direction, controlling while waiting for yaw rate to stop, etc. (even vortex ring state, in real life. It is stable enough and grown by adding thrust only in some wind tunnel experiments.)

Don’t you think that we should go a little further in saying that it is “over-used” and say that it does not mean a thing? It puts a fuzzy explanation on a couple of situations and does not give adequate interpretation to what may happen in flight and how to cope with it.

I would rather call LTE, for example: HICMTRDUHSAOTBFASAP, helicopter is a complex machine that requires deep understanding and high sensitivity and objectivity to be flown as safely as possible. Or, more precisely: MTCLTCWYR, Many things can lead to a crash with yaw motion.

Do you agree?

Name Withheld

Frank Lombardi Responds to ‘LTE versus NETR’

I agree with your assessment (and acronyms) precisely. Oftentimes, the concepts of power required versus power available are thought of without regard to the tailrotor, but it is continually part of the same equation. In fact, I may be repeating myself in saying that flying occurs only by virtue of a series of mathematical equations in balance. Ruin the balance of any one of those equations, and the rest of them will fail, in rapid succession, for very specific reasons as well. We as professional pilots are ultimately tasked with knowing our machine as intimately as possible—knowing its quirks and limitations so that we do not come up against them unexpectedly. My intent when separating the two phenomena was to slow down and differentiate processes that will happen in rapid succession in real-life, so that a pilot might better understand and therefore prioritize the managing of those balanced equations we spoke of. I believe the key point when referencing the aerodynamic causes and effects of LTE should be the emphasis on occurrences in the “normal operating envelope,” as over-pitching and drooping the rotor are certainly outside that.

Frank Lombardi, Rotor & Wing Contributor

From Facebook

The following comments appeared at: facebook.com/rotorandwing

(Responding to the image above of the Russian Helicopters Kamov Ka-62.)

Looks like its mother might have been Sikorsky and the father is of a new Bell design. Both related to Eurocopter and adopted by Kamov.

David Daly

Tail boom seems short.

Bill Doug Brockhaus

Bill, I would say the same thing. Maybe the tail rotor is very strong and efficient so the tail does not have to be that long. It seems like it take more power from the engines being so close to the fuselage due to the arm being short.

Timothy J Godwin

Correction

A Boeing Apache was misidentified as belonging to another manufacturer in “Investing in the Future,” on page 26 of the May 2012 issue. We regret the error.


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