How they Fly?

Frequently Asked Questions In Memory of Robert B. Wisler







Who invented the helicopter ? A lot of people !! , read the introduction and pioneers sections.



How the helicopter flies ? (or what happens if the engine fails ? or what does the pedals do ?) Well, it is quiet simple after all ;-) You will find several related articles in our how helicopter flies? section.





What is the biggest helicopter ? The biggest built was the russian (soviet) Mil Mi-12 Homer, and the biggest operational is the Mil Mi-26 Halo. Check them at the Mil timeline section. The biggest western helicopter is the Sikorsky S-65 / S-80



What is the fastest helicopter ? The current World helicopter speed record is held since August 6, 1986 by Westland 's Lynx at 217.5 Kts (402 km/h) using specially designed high-speed rotor blades.

In June 1967, a compound helicopter, the Lockheed 186 (XH-51) reach 487 km/h



How high can a helicopter fly ? The current World record is held since June 21, 1972 by the Aerospatiale Lama. Read the company press release at the news archives section.



Can a person make a helicopter by himself ? Yes, most ultralight helicopters are sold in kits. Read an article about ultralight helicopters



Where did the name and word Helicopter come from ? On 24th September 1863, Viscount Gustave de Ponton d'Amecourt used the word in a monograph entitled "La Conquete de l'air par l'helice. Expose d'un nouveau systeme d'aviation", published in Paris. In this 40-page document he put together the Greek words helico and pteron, meaning "spiral" and "wing", to make the word helicoptere. (Thanks Chris Jones)



Why are so many US military helicopters named after Indians ? Traditionally, Armed Forces choose a subject to give name to its ships, airplanes or vehicles. The U.S. Army aviation began in Ft. Sill, Oklahoma prior to moving to FT. Rucker, Alabama. Ft. Sill is located in the heart of many native american reservations and in honor of the location they decided to name helicopters after the various indian tribes. The one exception is the Bell AH-1 Cobra which was named such because the army did not want to offend the native americans by naming a gunship after an indian tribe and have the be percieved as an insult. Shortly thereafter many tribal leaders inquired as to why the Army stopped naming helicopters after indians. When the reason was explained the leaders stated that there are many aggressive indian tribes that are fit to name a gunship after which were the Apache, Kiowa warrior, and formerly the Comanche all got their names from.



Which was the first helicopter to be "LOOPED and ROLLED" ? The oldest proof that we had found is one by Harold E. "Tommy" Thompson, a test pilot of Sikorsky Aircraft.

He do it with a Sikorsky S-52 in 1949.



Why were "compound helicopters" not successful ? Read this article in our how flies? section.



When was the first time a naval helo made a rescue of a downed aviator ? The first US rescue was made in Feb. 1947 by (Jimmy) Viner, chief test pilot for Sikorsky Aircraft. The rescue was made with a Sikorsky S-51 helicopter.



Who are the Whirly Girls ? The Whirly Girls is a group of women helicopter pilots, like the Ninety Nines or International Women Pilots.



Which was the first helicopter used in combat ? This question is quite a debate. Check our Gunships evolution page and our stories section.



What is the name of the Russian helicopter used in "Raising the Mammoth" at the Discovery Channel documental ? Mil Mi-8 Hip and Mil Mi-26 Halo. Check them at the Mil timeline



What was the helicopter used in the M.A.S.H. television series? What helicopters were used for medical evacuation (medevac) in the Korean war ? Mainly, the Hiller UH-12/OH-23 and the Bell 47, and for transport, assault and SAR missions was used the Sikorsky H-19





How to pronaunce Chinook in English ? Steve, a former 2/75 Rangers tell us : Well, back in the early 70's, we had to walk off the back of these 2 bladed wonders. There is 2 ways to pronounce this aircraft;

1st -- for the legs that never jumped from them they call them the chi nook

2nd -- if you where a Ranger, you pronounced it shit hook :)



"Chi" with the 'I' being short

Boeing CH-47 Chinook Section



Which are the main reasons of helicopter 's aircrashes ? By far the greatest cause of helicopter (and fixed wing aircraft) accidents is pilot error. You can research this out for yourself at two US Government web sites where records of aviation accidents and the investigations related to them are posted online: Federal Aviation Administration and the National Transportation Safety Board



How many helicopters are there in the world ? As of 2001, the world helicopter fleet approximately is : (Source Aerospatiale)



Civil (about 26500 helicopters)

46.1% in North America

18.2% in Europe

12.7% in former Soviet Union

12.3% in Asia/Pacific

7.2% in South America

3.4% in the Middle East. 0.1% in Africa Military (about 29700 helicopters)

33.5% in North America

21.1% in Europe

16.6% in former Soviet Union

13.6% in Asia/Pacific

6.3% in the Middle East. 4.5% in Africa

4.4% in South America





Which is the growth in the helicopter industry ? As of 2001, growth in the industry as a whole over the next 10 years is likely to be very low, or possibly slightly negative, due to declining defence budgets and depressed civil markets. However, this is offset by the procurement of new models such V-22, EH101, NH-90, Tiger, over the next years to replace existing fleets.



Does the spare parts for military helicopters needs an FAA aproval, to certify their airworthness like civilian models ? Read about How long can a helicopter fly before it needs an overhaul in the how fly? section.



Which is the cost to become a pilot ? As of 2001, there a several factors ( type, country ) and would depend on what your goals / intentions are, but approximately us$ 8500 and will take around 5-7 weeks to complete.

Read an article about flight training considerations



What kinds of fuel are used in helicopters ? Most turbine powered aircraft, ie Jet Ranger, Huey, Bell 206, all use Jet Fuel (the same as an airliner) called JET A, JET A-1 or MIL Specs JP-4, JP-5, JP-8.

Piston powered aircraft use typical civilian av-gas (high octane AVGAS)



How much does the average helicopter cost to run per hour in fuel ? Fuel cost/consumption is an important element of operational cost, but to get a true picture of operational cost you need to include the amortized costs related to maintenance.

For example, as of 2001, the estimated cost of operation per hour for a Bell 206B is about $192; only $42 of that is fuel.



Is there a helicopter part called the "Jesus nut" ? Yes, it holds the main rotor onto the mast, you better be saying OH JESUS if that nut comes off because it is what holds the helicopter together.

You have a picture here from Butch "Iceman" 's Site





Which is the electrical power source (AC or DC) of helicopters ? Todays aircraft usually all use AC power, 115 volts, 3 phase,(either four wire, or three wire.) 400 cycle. Higher voltage allows less current, smaller wire, less weight, less heat. And because we live in the world of electronics today, AC is much better to control, but some equipment such as lights and some instruments still best use DC. (26volts). Therefore, most helicopters use both AC and DC. The accessory section of the x-msn (the transmission) drives AC generators which power all AC systems through a series of buses, etc.... and some of that energy is converted into DC through converters and they also have an all-purpose battery much like that of a car, for using electrical systems during system checks, and little applications without having to start and run the A.P.U. (auxiliary power unit) or engines.



What speed (RPM) does the average helicopter rotor spin ? Here are some standard Nr numbers:

Vertol 107 II/CH-46 - 264 rpm Aerospatiale 365/HH-65 - 355/365 rpm (variable) S-61/H-3 - 247 rpm S-70/H-60 - 258 rpm



Why do you pilot a helicopter from the right hand seat, while in a plane it is from the left hand seat ?

We can list several reasons : - In the early days of rotorcraft development, the machines that flew then did indeed have a distinct difference in altitude between the left and right sides. The left side of the aircraft, at a hover, was considerably lower than the right side. Therefore it was determined that the right side should be the pilot's seat. If the rotor system turned in the oposite direction the effect would be reversed.





- Generally, technical reasons choose the pilot seat.

Have a look at the Robinson R22, due to the rotation of its blades, it would fly inclined on the left .

the right blade is the fastest one when flying : it speed is the rotation speed plus translation speed



The left have it speed equal to : rotation speed minus the translation speed.

Also the fuel tank is on the left side. So, the pilot has to be on the right side to equilibrate the system. On a big helicopter, this effect is minored, but on a light one as a R22, it so important that the helicopter could not fly.





- Other reason that the pilot position is on the right is because the pilot needs his right hand to fly the A/C. Since the collective doesnt need the attention that the cyclic needs its only natural to put the pilot on the right hand side, thus leaving the left hand to tune radios and perform other tasks.





- another very simple and logical answer: in earlier helicopter models, and in most of today's smaller models, having the collective stick on the left side made it awkward for the pilot to enter and exit his seat, having to step over the collective control stick either way. Thus entering and exiting from the right side made more sense. Plus, it simplified the collective control linkage system.



On some helicopters there is a long, forward-angled protuberance mounted just above the front windshield and below the rotor. Can you tell me what this thing is ? It's a wire cutter. It's designed so that if you hit a wire or cable you cut the wire. It's a safety feature designed to provide some protection from wires or cables when flying at very low altitude. Of course, to be effective, you must hit the wire at exactly the right height





What causes the whop noise that can be heared from along way off? The whop noise is actually caused by a slapping movement end of the rotor blade...not from sonic booms. In fact, when a blade tip approaches the speed of sound, very bad things happen as the aerodynamic properties of supersonic flight are very different than subsonic. The problems encountered with helicopter airfoils as they near the speed of sound is one of the factors that limit the forward speed of helicopters in general.

Thanks Todd Vorenkamp







Is it possible to make a chopper "quiet" ? So you only hear him when he's just right above you. Often seen it in action movies - but is it possible ? There is no button to activate a "quiet mode" yet but there are technologies such as canted rotor blades, offset pairs of blades, shrouds for exhausts, etc, that cut the noise level by as much as half or more.

The NOTAR ( see the how flies? ) is one of the quietest of all -- eliminating the tail rotor and its 360-degree pattern of noise dispersal literally removes one entire sound source.





How long can a helicopter stay in the air without moving around ? Yes, it can hover in one place until the fuel runs out or the pilot gets exhausted which ever occurs first. It takes more work to hover than in any other mode of flight, unless of course, the aircraft is equipped with hover hold.

But trust me, you do not want a helicopter to hover over your house long ;-)



I recently flew in an helicopter in very poor weather. A fixed wing aircraft would have been buffeted quite badly but no noticeable turbulence / buffeting was evident in the helicopter. How come ? Or was it just good airmanship ? The fixed wing of a fixed wing aircraft is exactly that, fixed. The turbulence and buffeting is not absorbed by the wing. All of the turbulence in the wing is transferred directly to the fuselage of the aircraft.

In helicopters the rotor system flexes during flight. The blades can sometime flex as much as 2 or 3 feet during flight and much of the turbulence is dampened out before it reaches the rotor hub. On many aircraft the hub also flexes in unison with the blades.

Some aircraft have additional computerized flight control systems which assist the pilot and make automatic inputs to the flight controls.



Plus ... helicopter pilots are heads above their fixed wing counterparts when it comes to airmanship ...





Why it is necessary to earth a man when descending from the helicopter to the deck of a ship that is made of reinforced plastic ? All aircraft generate large amounts of static electricity; it's caused by friction of the air moving over the wings and other surfaces. If you check the trailing edges of commercial airliners, you will see what look like small antennas or small ropes attached that allow these charges to dissipate. Helicopters are huge static generators; the larger the helicopter, the larger the charge. Even if the deck of a ship were made of non-conducting plastic, that static charge has to drain off somewhere, and it usually drains right into the shoes of whichever unlucky fool is the first one to grab the external cargo.





Is there any relation between the size of the helicopter and the landing pad, or is it a specific ? The landing pad size for a helicopter is that it has to be larger than the rotor blade diameter plus the tailrotor diameter and the depth of the pad meaning the height of the trees surrounding the landing area. Next you have the weight and power remaining to determine.



E.g. if the helicopter is light, has alot of reserve power, and has to hover down into 50 foot tall trees with only 3 feet of clearance between the blades and the trees, it would fit. If the helicopter is heavy with payload and unable to hover out of ground effect the helicopter would not even attempt.



How much is the maximum weight for an Ultralight ? You must always have a look to the Federal Aviation Administration website.



As of 2001, Regulation Part 103 :

For the purposes of this part, an ultralight vehicle is a vehicle that

(a) Is used or intended to be used for manned operation in the air by a single occupant;

(b) Is used or intended to be used for recreation or sport purposes only;

(c) Does not have any U.S. or foreign airworthiness certificate;

and (d) If unpowered, weighs less than 155 pounds ( 57 Kgs ) ;

or (e) If powered (1) Weighs less than 254 pounds ( 94 Kgs ) empty weight, excluding floats and safety devices which are intended for deployment in a potentially catastrophic situation; (2) Has a fuel capacity not exceeding 5 U.S. gallons ( 19 Liters ) ; (3) Is not capable of more than 55 knots ( 101 Km/h ) calibrated airspeed at full power in level flight; and (4) Has a power-off stall speed which does not exceed 24 knots ( 44 Km/h ) calibrated airspeed.



























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