Helicopter Cowboy Image

[sierra-papa]

I would like to start a discussion in reference to Deep C's thread called "Exessive Rotor Downwash". Deep C is not a pilot, but rather represents the common public and their opinion about us. I guess he was not the only one witnessing the two scenarios. There were probably hundreds more, all of which did not come on this forum and get answers to their questions. Unlike Deep C, they probaly walk around at this very moment and think that all helicopter pilots are just shortsighted cowboys. Even if non flying observers don't know all the facts and the decision making process in a busy cockpit (especially where a crew is preparing for a low level - off airport op), nevertheless they are forming the public opinion and also anti helicopter lobby's. Now it's these very same people that stand for the majority of our helicopter industries market.
Not a single one of the posts took an angle at what we can/should do to better our image and thereby increase the market we operate in. Is this maybe because we really do not care about how we affect our surroundings??
Time back I instructed out of a medium sized airport in Florida. One day 2 Army helicopters came in for gas. Before they set down they managed to flip a Cessna 172 upside down, and when they left they hovered for ages over the most dusty spot at the airport - upwind of the ramp - kicking up a cloud of dust/grass and trash. All of which settled nicely on all the airplanes parked on the ramp (there were Citaton 10's and the like with open doors). It took us (the few helicopter pilots there) weeks to calm down people because of this incident. Another example (which probably many of us have seen in the news) happened 3 weeks ago in Italy where 4 or 5 US helicpoters flew so low over the beach while beeing ferried, that they turned a entire beach restaurant upside down - injuring several people with flying debris.
I hope for the pilots sakes that they in hindsight have learned their lesson, but the damage to our image will take a lot longer time and also effort of all of us to balance.

[Randy_g]

This problem is endemic to our industry. It seems there are a great many who fly helicopters who have no idea of what their downwash is doing or causing. What most seem to forget (or are ignorant of) is that the heavier the helicopter, the more air we push down, and out. An R22 can get away with flying low and slow over a building, beach, etc. without causing a big ruckus. Do that same thing in a Bell 205, or Sikorsky S61 and you can cause a big mess.

When I first flew Bell mediums, I was guilty of not paying attention to my own downwash. Until someone more senior chewed me a new one (and made buy the beers all night) for not thinking about/caring where my downwash was going. I had just transitioned to the medium from a light helicopter where the downwash just didn't matter, as it was so light. Had I started thinking about it when I first started flying, it would have never been a problem. Always pay attention to what your downwash is doing, because as pilot in command you are responsible for any damage the operation of your a/c causes. If not legally, then morally.


Cheers

http://randyspics.tripod.ca/gifs/naughty.gif Randy_G

http://randyspics.tripod.ca/gifs/bear_eating_picnic_md_clr.gif

[Grainger]

A big part of the problem is education: members of the public just don't understand that a large helicopter has to shove several tons of air per second towards the ground to stay in the air. They are then very surprised when they do encounter downwash first hand.

The popular explanation of aerodynamics is largely to blame for this - everyone is told about the pressure being less above the wing and greater below it. This is usually presented as some magical process brought about only because of the precise shape of the airfoil.

Very rarely is it mentioned that this also results in the air getting pushed downwards - that's the boring part of the explanation; accelerate the air downwards and you'll go up. Much more exciting to make yourself sound clever going on about Bernoulli and so on.

Schoolteachers up and down the country take note.

[Bronx]

sierra-papa
I know what you mean, but my British friends seem to have a much tougher time than we do. In the UK, the low flying rules are a lot stricter than in the US, and people are very quick to complain about helos. Even their SAR and EMS pilots get complaints about noise and low flying. :rolleyes: Problem seems to be that instead of supporting the industry the British CAA jumps when the anti-aviation complainers whistle. Maybe they should try to educate people to accept helos and not complain so much.

[Helinut]

I am told the CAA are also intending to sponsor a flying pig display next year at the Biggin Hill Airshow ;) :rolleyes:

[johndrew]

I have to agree with Grainger on this one. Although not yet a rotary wing pilot I have been in and around them for some years as a skydiver. (yes I choose to jump out of them).
Earlier this year at a parachute display the RAF had bought in a Chinook as a static display. This was, of course, very popular with the public who were allowed to climb around it and ask the crew very important questions like 'Why does it have two fans?' (Answer:'we keep one as a spare in case the other breaks').
When it came time to leave the site the crowd was being held back by police officers and marshalls. While the engines were turning and burning the crew were trying to get the crowd moved back. It was like King Canute trying to stop waves coming ashore. I could see what was going to happen and even though I tried to assist to move the audience back, the crowd dynamics took over and in the end I retired to a safe distance behind them. Of course when the collective went up, some of the crowd went down. What can be said afterwards except 'We did try to warn you but you didn't want to listen'.

[sierra-papa]

Grainger,
I think we will wait a long time before schoolteachers feel the need for educating kids about rotor downwash. Not that it would hurt, though. But I think (and agree with Randy_g ) that we must educate our own people. Situational awareness is an under estimated issue in both helicopter and f/w instruction. I am still teaching CPL's and CFI's besides my corporate job, and you can be sure these things are on the agenda.

Bronx,
I hear that it is the same in the other parts of Europe. If we dont change some of our behaviour as pilots then we'll have to face the same here in the US. It's getting more crowded everywhere. Which brings me back to the point of the tread: we are hurting our own bussiness if this things are not addressed.

[Q max]

If you upset 10,000 people by one 10,000th of a vote - then you've cancelled your democratic right to fly.

Make Mr Public happy - take them flying sometimes and sell the helicopter concept - win votes.

Mindless 'Jocks' flying their bosses shinney muscle chopper over cities at 800 feet pulling Max continuous and Vmax : 1,000,000 people by one thenth of a vote - 100,000 votes lost - does a lot of damage.

Gotta put something back in - save lifes - do kids visits/rides - that kinda thing...

[sierra-papa]

Q max,

"Gotta put something back in - save lifes - do kids visits/rides - that kinda thing..."

- good thought, luckily the people I fly for right now see this the same way - so I can actually do that. Anybody that has been given a fun ride once seems to be cured of the anti helicopter syndrom for a long time.

"Mindless 'Jocks' flying their bosses shinney muscle chopper over cities at 800 feet pulling Max continuous and Vmax : 1,000,000 people by one thenth of a vote - 100,000 votes lost - does a lot of damage"

- do you really think that 800 AGL is annoying (for somebody on the ground)??

Everybody,
Are there any statistics about helicopter noise. Any good article on how to fly neighborly?? Noise abatement??

[S76Heavy]

I usually slow down when coming onshore after a flight. From 143 to 120 Kias means a drop from 80%Tq to about 60-65, bound to make some difference and I don't lose too much time either.

[Q max]

Yea 800 is high in usa - but low in europe
- 'go figure' .... (>1/4 that noise at 1600')

[SASless]

I believe one could build a heliport in the middle of the Badlands in South Dakota....with not a single structure or human within 75 miles.....and within 24 hours have noise complaints. We had a downtown heliport....just off an interstate highway....and a railroad track......we used the heliport no more than three times per week....and had the neighbors complain about the noise despite the approach path and departure path being overhead the highway and railroad. I ask you....does a MD-500E make more noise than a one mile long freight train or a major urban highway? The vibration from the train alone....would be more a nuisance than the racket of the helicopter. The same neighbors also tried to shut down the EMS operation further down the road....despite the "lifesaving" nature of that operation. It just reminded us of why we displayed the "Please do not Cali-fornicate Oregon! " bumper stickers.

[Jeep]

To whom does the downwash belong?

The recent Daily Mail headline of 'Woman blown 20 feet in the air by Helicopter' caught my eye for a few reasons: Was she made of paper? What was a heavily laden Chinook doing at a hotel? Having now read the article and researched the incident, mainly with the use of PPrune, it would appear my initial questions were only the tip of the rotor stream and certainly not a slice of poor Wokka airmanship.

I have been involved with helicopter downwash for some 25 years now. As a ground crewman it was no fun to erect my 9x9 command-post tent only to have some oik Gazelle pilot land upwind of me and turn it into a kite, normally with me attached as an anchor. Or as an aircreweman stationed in Northern Ireland, when the Armed Forces Minister Archie Hamilton insisted we landed in front of the company of soldiers at Ebrington Barracks with a strong westerly blowing across the Foyle. How well their riot gear, all neatly laid out in front of each soldier, flew to the opposite end of the square. Even my last tour of duty in the Emerald Isle; how many times have i witnessed; flying corrugated metal sheets, Wessex blades rising up and down like Muslims at prayer time, and parked cars that qualify for the free grit and sandblast because of their proximity to the landing site?

So just who is responsible for downwash? In my opinion, it is the aircraft captain. It is the equivalent of jet-blast, tractor mud and toenail clippings; YOU create it, YOU dispose of it.

How fast in MPH is the fully developed rotor downwash (remote wake) of a hovering helicopter? Lets take a Lynx at MAUM (10750lbs) in nil wind conditions. Try a guess at the downwash speed;

a. 40kts

b. 70kts

c. 110kts

A gold star for all those that got answer b. If we take the same criteria for an Apache at 17500lbs some 65% heavier then is the downwash speed the same magnitude higher? Have another guess:

a. 75kts

b. 120kts

c. 160kts

Luckily for our ground crew, tent erectors and hairdressers the answer is a.

The downwash velocity increases again when hovering in wind. Using Pythagoras and a 30kt headwind, the downwash horizontal vector for our MAUM Lynx now increases to 76 kts. More importantly it is directed behind where it can devastate unseen! Try an experiment next time you have the following props: wet runway, headwind, hovering helicopter. Hover IGE into wind and note the disturbed water eddies on the runway in front of you and then turn downwind. Note the increase in distance you can see the disturbed eddies. It is this horizontal movement of the downwash that often catches pilots unaware. It certainly was a factor in the Daily Mail incident.

So what should the caring, careful, airmanship meister do, to minimise his destructive downwash? Adhering to the following list should help:

a. Conduct a recce and observe downwind of your intended landing/hovering point before landing (make it a 6 S recce (Size, shape, surrounds, surface, slope and security - of surrounding structures).

b. When hovering, about to hover or hover taxiing, look around for likely problems, particularly downwind.

c. Know your aircraft weight, downwash strength and direction, and wind strength.

d. Be responsible for YOUR downwash.

An old sweat once said to me "If you mean to blow the tent away it is amusing to succeed. Iif you didn't it is poor airmanship and likely to get your nose punched!

Feel free to refute the maths and pick holes :)

[sierra-papa]

Hi Jeep,
I couldn't agree more with your post. I like the humor, too. :) Why is it, you think, that so few of us are sensitive for this kind of stuff. We seem mostly to be nota hair better then f/w pilots (who don't care about jetblast/propwash).
sp

[Q max]

...are you sure the downwash velocity isn't reduced in a Lynx when you move through the air at 30kts?

[Jeep]

Max Q,

You are of course right.

Maths aren't my strong point, and feel free to quote the correct figures. I'm rather pleased you only mention the pythagoras point, does that mean the rest of the maths were about right?

[Q max]

:)

[CyclicRick]

Jeep and I are obviously from a similar background (AAC groundcrew trained), mostly because most of his advice is straight out of the groundcrew manual of which I still have a copy, a shame it's not more widely available because it's a sound piece of work.
Downwash is a reality and can be a problem, it can also be grossly exaggerated. I fly 205's amongst other things and we do a lot of sling loading including some pinpoint constuction work, forestry fertilization etc. with weights well up to the 10,500lb limit.
We use a 10-12m strop for most of the work we do and I've stood underneath when helping out on the ground.
The downwash dissipates very rapidly and loses velocity with gained height and at about 30ft it's like a windy day even when stood out to the side.
The closer you get to the ground (ie landing) the stronger it is and that can br pretty windy, fair enough.
I've heard/read about the story of the lady being blown 20ft by downwash, the helicopter involved was a AS 355. Try it and you will see what a load of rubbish that story is. Don't ask me what the motives were to dick the pilot like that but I have a few ideas.
I still have to agree with most of you though, you have to be careful what you do and how, there is always someone out there who wants to complain, ( I work in Germany and they are quite professional complainers) justified or not, and 9/10 YOU as captain will pull the short straw.

We live under a permanent barrage of noise complaints but there are limits to what you can do no matter how careful you are!





:confused:

[The Nr Fairy]

CyclicRick :

The main thread I could find on this one was

20 feet or 6 inches (http://www.pprune.org/forums/showthread.php?s=&threadid=19347) - seems more like a pilot's girlfriend's musing to me.

[nushooz]

Re : Sierra - Papa's comment on the big coporate guns low flying

the biggest civilian offender in the noise department seems to be the Augusta 109 - even @ 2000 ft+ and regardless of pitch etc - it's quite amazing how much noisier than squirrels, 206s EC135 etc. When it is coming towards you you can hear it miles away, yet once it is over the top it , it's not bad at all.
How did they manage to make something so loud - thought that honour always went to military choppers only:)

[sierra-papa]

nushooz

ooops! Agusta is what I fly as backup!! Didn't know they were so loud. Where can I find the source for that info? sp

[Rob_L]

Best demo of downwash I ever saw was when the captain of a dead BO 105 was admiring the sight of an SA365C on approach with a maintenance team. The downwash from the 365 lifted our hero off his feet and into the safety catch net surrounding the helideck, next stop would have been 70 feet down into the North sea. Bet he never stood there again.

[nushooz]

SP

'fraid no data, just listening out when walking the dog !!

- although it was a topic for discussion here 0n 15th Oct 2001 where "noise footprint" was discussed in detail

http://www.pprune.org/forums/showthread.php?s=&threadid=19869&highlight=NOISE

regards

[Qualityman]

I had great pleasure in being allowed to Marshall the EH101 at Helitech 3 years ago, and much to the amusement of my colleagues and the aircrew, I learnt what an incredible Downwash that heli has. I was blown 20 feet across the Tarmac into a double skinned and propped security fence, four lengths of which went over with me.

I then had even greater pleasure the following year at Farnborough International 2000, when the same aircraft took out just as much fencing, two press photographers, a local constable and two cars parked in the wrong place, despite having given the display management a warning of the ferocity of the Downwash at a planning meeting.

What a monster !