Wednesday, June 1, 2005
Help With Brownouts
With all due respect to Lt. Col. Steven F. Colby and his fellow military aviators, after reading his article on better ways to deal with brownouts, I couldn't help but make some comments ("Help With Brownouts," March 2005, page 42).
I have more than 30 years of commercial helicopter flying in a utility role in some of the harshest environments Mother Nature has to offer. I have never had the luxury of autopilots or any other form of stabilization. Thus, I was taught early on to use procedure to keep visual cues alive, especially during takeoff and landing.
There is seldom a reason that a normally loaded helicopter with skids couldn't take off and land in loose dust and snow without loosing visual reference. A helicopter with wheels turns seldom into almost never. The key is to not begin and end every flight with a prolonged hover.
On takeoff something as simple as a vertical stake in the ground will work long enough to transition to forward flight. I was taught to terminate every approach to a landing just in case I didn't have enough power to do otherwise. Shooting an approach to an exact spot uses that same annular flow the colonel was talking about to your advantage. The dust or snow tends to flow out, leaving better vision next to the helicopter. Without a small piece of permanent vegetation, a vertical stake has guided many heli-ski and other pilots to a safe arrival.
The military has always made a point to avoid or limit operation of aircraft in hostile environments. I submit that limiting their time outside of translational lift will have the same net effect as limiting their time in a battlefield. Based on the numbers Colonel Colby used, hovering in sand is far more dangerous.
Don't get me wrong, I like fancy technology as well as the next guy. It just seems to me a procedural solution exists now for a lot less money.
ASMEL Rotorcraft Helicopter
Steve Colby responds: I have to disagree wholeheartedly. I, too, have flown in the world's harshest environments, albeit for only the past 25 years, and have tried every trick in the book to stay out of the cloud. I can say unequivocally that it is impossible to stay out of the cloud with zero forward-airspeed touchdown in a low- to no-wind environment, especially in Afghanistan. This for military helicopters is a function of disk loading, which in Mr. Thomas' birds has been relatively low.
Impressed With Flirs
Your article on firefighting came out just as I was working with FLIR Systems on an airworthiness certificate for their multi-sensor camera mounted on a Bell 206 L3 ("Bigger, Faster, Better--Same Price?," March 2005, page 18). I was asked to ride along on one flight (not for purely technical reasons, but because I was a convenient movable shot bag for weight-and-balance purposes). When I saw what a great presentation could be seen using all of their ball-mounted sensors, I realized more people in the firefighting world should be exposed to forward-looking infrared sensors' capabilities. As an example, from 60 mi. away, we could zoom onto Mount Hood and clearly denote the glaciers and other features on the mountain. I thought the IR and visual optics were fascinating.
I previously worked for a heavy-lift logging and firefighting helicopter company, but GPS was the best we could use at the time. A gyro-stabilized flir may be able to stand up to the heavy translational vibrations expected on the crane-type helicopters. It should be added ASAP.
Possibly Rotor & Wing should present an article about the use of this system not just for firefighting but for so many more applications, like a miniaturized system to be mounted in police cars for child/criminal searches, just as helicopters are used for that today.
As you can tell, after seeing the system in operation, I believe as Tony the Tiger says: "It's Great!"
Designated Airworthiness Representative
Central Point, Ore.
Best for the President?
With all the talk of speed, range, lift capacity, security, and homegrown content, one big question was never answered in the whole selection battle for the U.S. VXX presidential helicopter program. As a pilot, a businessman, an investor, and a taxpayer, I would really like someone to tell me this: Why does the president need 23 helicopters?
I know that $6.1 billion will do a lot for Team US101, but just imagine what else we could do with some of that money. Personally, I'd rather buy him a baker's dozen and then put the rest of the cash into building some downtown helipads that we all could use.
San Jose, Calif.
According to Douglas Isleib, U.S. Naval Air Systems Command's program manager for presidential helicopters program, 23 aircraft are needed because of "the global nature of the presidential support mission." This number allows for aircraft to be ready to fly the president, the vice president, foreign heads of state and other Defense Dept. officials within the U.S. capital region, and to meet maintenance, upgrade and pilot/aircrew training and proficiency requirements.
Engine Failure Particulars
Regarding Shawn Coyle's article on practicing emergencies, I would agree in principle ("The Reality of Turbine Autorotations," April 2005, page 62). It is true that simulated autorotations--if any--are performed with an eye toward avoiding damage to the helicopter and mostly with due respect to the height-velocity curve. I've heard from helicopter types who are not even permitted to conduct "real" autorotations due to risk of damage to the drive or gear.
I do not agree with Mr. Coyle's assessment of remaining engine power to the drive while throttling down to idle. The only effect will be a reduced friction within the free wheel unit (especialy on helicopters with single-shaft turbines like the mentioned Gazelle or Lama) due to the reduced rpm difference--which is hardly measurable--and the residual exhaust thrust of a few pounds. This should not reduce the rate of descent by that mentioned amount.
Mr. Coyle is completely right in emphasizing the human factor of surprise if any sudden malfunction happens in flight. So, consequently, one has to be ever alert while performing special missions that are close to the height-velocity curve borders, such as surveillance, power-line inspection or construction.
I remember vividly an incident during power-line stringing in 1976 when I happened to have a split rpm. indication on my Alouette 2 while hovering in 150 ft agl. close to a tower.
Luckily it was the first tower before crossing a large forest and so the consequent autorotation after hook release brought me well clear. Only after applying collective pitch did I learn that the turbine was still performing. Ground inspection revealed a broken drive shaft to the turbine rpm generator.
I had no time to count my pulse rate as I had to pick up a standby helicopter from our nearby base to continue the mission after this un-scheduled short break--and I finished in time.
Capt. Uwe Heins
Whilst Shawn Coyle does us a service by pointing out that practice engine failures may not be like the real thing, I'm not sure about some of his reasoning. Shaft horsepower is shaft horsepower. By definition, it is measured at the shaft and is zero with the needles split (or the rotor stopped, but don't try this in flight). Thus Shawn's statement that we get 20 shp at idle is impossible.
If the hydraulic pump is on the engine, sure, hydraulic power is still available when the needles are split, but that power is to aid the pilot in operating the controls and isn't available to the rotor. If the hydraulic pump is on the rotor side of the one-way clutch, hydraulic power is still available if the engine fails. In both cases the autorotation performance with engine on or off will be the same once the needles are split.
However, in autorotation, the engine exhaust goes up through the rotor and the heat reduces the air density. At idle the efficiency of a turbine is zero and the whole fuel burn is converted to exhaust heat. Thus, if there is a difference between engine-idle and engine-off performance, it is more likely due to exhaust heat.
I wouldn't have thought the effect was that great, and the pilot could easily overcome it by reducing the rotor rpm, which extends autorotation performance significantly.
Mr. Watkinson is the author of "The Art of the Helicopter," published by Elsevier Books.
I was surprised to read the article from Lt. Andrew Severson with reference to the commercialization of military search-and-rescue units (Feedback, March 2005, page 7).
I am a ground engineer and my discipline is avionics. During my term in the Royal Navy, I spent a few years with a military SAR unit based at HMS Gannet in Prestwick, Scotland. The concerned unit was 819 NAS and it secondary role was SAR, despite that it was virtually guaranteed that we would be called upon to launch a helicopter at 15 min. notice, which we always seemed to be capable of achieving.
The aircraft at that time was a Westland Sea King HAS Mk.2. whose primary role was helicopter anti-submarine location and destruction. We had a hydraulic hoist attached to the aircraft for use in military and civil SAR operations. The crew, including the ground staff, were highly trained to carry out these operations. After nine years of service, I decided to join the civilian helicopter sector, working in the North Sea, and I can assure you that crews working within that environment are more skilled than their naval or air counterparts.
Most of the crews anyway come from a military background and have the relevant experience and training necessary to carry out multi-tasking within hazardous environments.
Moving to British Airways at Sumburgh in the Shetland Isles was my first crack at supporting a civilian SAR Unit. The crews were mostly ex-military like myself and knew what was to be expected of them. We supported the Sikorsky S-61N, which proved time and time again that it could carry out its tasking day or night.
After that, I moved to Aberdeen with Bristow Helicopters. At that time the company was very keen on training their engineers and I gained enough experience on types like S-61N, Bell 212, Bell 206, S-76a, AS332L, and SA330J to enable me to support a SAR unit based at Stornoway, Isle of Lewis, Scotland. We only had one aircraft, with a backup based at Shetland.
Because of the aircraft and the equipment chosen, along with the experience of the engineers, we very rarely needed to use that second aircraft while I was there, which was for a period of six months. We had 100-percent serviceability at all times.
This pleased the coast guard and today I still believe that Bristow Helicopters are continuing with the commercialization of SAR Units, which in my experience show that, within the United Kingdom, this is a good move as it releases military aircraft to carry out their assigned military role.
Do not misunderstand me. The SAR role for the military is still a viable one and should never be totally civilianized. To all you military pilots out there, the job you do retrieving aircrew from the oceans and the deserts of the world will always, I hope, belong to you and could never be taken over by a civilian company.
Licensed Avionic Engineer
Royal Flight Oman