Saturday, May 1, 2010
Feedback May 2010
President’s Offshore Plans
During a speech on March 31 at Andrews AFB, U.S. President Barack Obama unveiled plans for “the expansion of offshore oil and gas exploration, but in ways that balance the need to harness domestic energy sources and the need to protect America’s natural resources.” His administration is considering areas for drilling “in the mid and south Atlantic and the Gulf of Mexico, while studying and protecting sensitive areas in the arctic. That’s why we’ll continue to support development of leased areas off the North Slope of Alaska, while protecting Alaska’s Bristol Bay.” Noting that there will be both detractors and supporters, Obama said that “the answer is not drilling everywhere all the time. But the answer is not, also, for us to ignore the fact that we are going to need vital energy sources to maintain our economic growth and our security.”What is your take on the president’s plan? Will it affect your operation? Send a note to firstname.lastname@example.org and we’ll include your thoughts in a future edition.
Ring Vortex 101
I would like to submit feedback to “The Dream Machine” article in last month’s issue (see Rotor & Wing April 2010 print edition, page 30), providing some clarity to the article and flight testing emphasis of rate of descent contribution to the ring vortex. I hope this will provide some insight and help to operators.
High rate-of-descent does not cause high energy ring vortex or “settling with power” as suggested by the article and flight testing. However, it happens to be the only measurable parameter in flight available for warning to the pilot or flight computer of a high energy ring vortex condition.
The parameters necessary for a high energy ring vortex to occur are: forward speed below translational lift (preferable 10-20 KCAS); decreasing rate-of-descent (example 1,200 fpm to 800 fpm); high gross weight (maximum rotor pitch); and low density. These conditions all add to increasing the energy of the ring vortex, by increasing the circular vortex velocity and decreasing the vortex diameter (tighten the vortex). These are the conditions required for a rotor. Then add the problem of the V-22 being a mixture of a rotor and a propeller with lateral positioned rotors, results in the uncontrollable condition. The pilot’s natural reaction to correct the loss of roll control in the V-22 is to control a roll in the opposite direction adding higher pitch, which intensifies the condition. The V-22 can enter a “high energy ring vortex” condition at descents of 500 fpm if all the conditions above are applied. The rate-of-descent “warnings” and flight computer automatic control responses are the best the designer can achieve, but not a valid system safety prevention for the adverse conditions of flying in a high energy ring vortex or settling with power condition with the V-22. Rotors are always in a ring vortex state when flying below translational speed in a descent. High rates of descent are not the cause of developing the high energy state of a ring vortex.
LTC U.S. Air Force (Ret.)
Editor’s note: Mr. Eastman is a graduate of the USAF Aerospace Test Pilot School, with a masters in aeronautical engineering and a masters thesis on rotor wing ring vortex. He has more than 8,000 flight hours and is qualified in 27 helicopters.
Richard Whittle responds:
My description of vortex ring state in “The Dream Machine: The Untold History of the Notorious V-22 Osprey” was reviewed prior to publication by aeronautical engineers and test pilots who have studied the phenomenon. I stand by it. —Richard Whittle
I don’t mean to be critical, but Charlotte Adams did more to confuse than to clarify in her March article (“EMS Safety Awareness Up But Wave of Regs Expected,” page 32) regarding A021. She wrote: “A021 also encourages IFR operations by allowing operators to use weather reporting within 15 miles of the destination area or an area forecast if the former is not available.” Thanks... for not aiding in our understanding of this aspect of A021 “encouraging IFR operations.” Overall, thanks for increasing our awareness on this issue and the NTSB’s Most Wanted list.
Springfield Engine Shop
To clarify a misleading headline (“StandardAero Springfield to Reopen,” appeared online March 26), StandardAero’s 225,000-square-foot Springfield facility never closed. What closed a few years back (as Landmark Aviation) was the turbine engine shop, much to the dismay of employees and customers alike. Our otherwise full-service facility will restart an MPI shop for TFE731 engines this year. It’s the first step back to the extensive capabilities we lost when the full engine shop was broken up and moved to other Landmark (now StandardAero) facilities.
Service Department Maintenance Tech
StandardAero, Springfield, Ill.▶ R&W’s Question of the Month What is your opinion on the U.S. President’s plan to expand offshore oil exploration?
Let us know, and look for your and others’ responses in a future issue.
Do you have comments on the rotorcraft industry or recent articles and viewpoints we’ve published? Send them to Editor, Rotor & Wing, 4 Choke Cherry Road, Second Floor, Rockville, Md. 20850, USA, fax us at 1-301-354-1809 or e-mail us at email@example.com. Please include a city and state or province with your name and ratings. We reserve the right to edit all submitted material.