Autos with wheels
 

Do helis with wheels travel much further than aircraft fitted with skids on ground contact during autorotations?

Not if you have the brakes locked.

But then the tires turn into Italian Gumm-A's that go" whoppa whoppa whoppa whoppa" as you taxi at any real speed.;)

Thanks for the quick reply SASless, but any chance it could come with a translation?

I would suggest it will depend on the surface and the effects will vary widely.

Assuming there is a reasonable foraward speed, say 25 kts?

A skidded a/c will travel a long way down a tarmac runway, whereas a wheeled a/c would be able to stop quickly,

On a firm but wet grass surface I would suspect the skidded a/c would stop a little quicker as the wheeled a/c will probably skid but have less surface contact.

On a wet soft surface, the skidded a/c will stop very quickly if you lower the lever quickly and the wheeled a/c may well dig in and come to grief.

SASless, you don't need to do an Auto to land with the brakes locked!

No direct answer but just a thought:
I would think that skidding for some distance is actually good news as it serves to slowly disipate the forward energy.
If you landed with wheels locked onto tarmac then the shock loadings would be much greater.

In the Whirlwind 10 it didn't matter, brakes on or off same effect. This was a helicopter that taxied like a shopping trolley as it had a wheel at each corner.

HF

Did the old Whirlwind have bungee cords for centering the forward wheels as did the H-19? Running takeoffs in the Hog 19 were a treat....until the front wheels started shimmying....just like that shopping cart you refer to.

Squirrel....complicated techincal discription of the situation I described in Bubba-ese. If one were to lock the brakes on a wheeled aircraft...then execute a run-on landing....the resulting friction of the macadam surface acting against the tire (tyre) would remove a bit of the vulcanized compound which the tire (tyre) is made of....thus leaving what is commonly known as a "flat spot". Then upon releasing the brakes....and ground taxiing away....one might then hear a "thumping sound" as the flat spots impact the surface upon which the aircraft was rolling on.

;)

212man.....I usually did a wheels locked landing when I forgot to release the parking brake after the rig takeoff. And I was young in those days.

Also...touchdown auto's in a Chinook were great sport....zero ground speed touchdowns were a real challenge....but not as challenging as touching down at 60 knots GS.

SASLESS....Touchdown in a Hawk @ 60KIAS was easier than landing a C150.....................and thats with one eye closed and the other one shut!:p Don't mess with the parking brake unless you are Parking or doing slopes.............

SASless

We do approaches to a sort of botched up ramp area thats not quite a helipad and not quite Cat B - sort of a hostile exposure type thingy

Anyway some of the pilots make their approaches brakes off - I don't, figuring that when I hit LDP and something happens I'll be pushing the pedals through the chin bubble anyway - guess it takes a little of the work away.

Never actually did a run on brakes locked though - sounds interesting.

If you are doing an auto in a wheeled (twin) aircraft, the least thing you are worried about is wearing a flat spot on the tyres. Something else has gone seriously wrong, and it will be very expensive to fix. Some Dunlops will be the cheapest thing to replace, after the soiled lambswool seat covers.

Watch out for the low tail of a 76, you will slow the beast better with brakes than by aerodynamic braking. Blackorks and Seahorks have the advantage of a tailwheel to save the boom scrape.

AC,

What was that about tail boom clearance, Clarence? ;)

http://www.helicopterservice.com.au/...20Nov%2002.jpg

Squirrel,

Thereis no contest, wheels take it every time for most ground operations, especially running landings and autos. The only advantage of skids is obvious and important, especially for light helos, they are cheap, light and simple. Otherwise, skids are a pretty poor but acceptable:

1) Running landings. Skids are troublesome, as there is really no control over your motion, just some uncontrollable friction. No brakes, and no steering. Wheels provide all that, and also have the ability to move for miles without wearing out.

2) Ground movement. Wheels allow taxi operations with very little rotor wash. Skids require hover liftoff for everything. By about 10,000 lbs, hovering helos are simply painful.

3) Broken ground. A tricycle gear wheel configuration fits almost everywhere, including broken rocky terrain. Skids require that two parallel straight surfaces be found before the aircraft can be landed, let alone shut down.

4) Maintenance. Skids are dirt simple, and take the prize.

5) Weight. Skids are very light, and also cheap to manufacture.

6) Crash attenuation. Generally, wheels and struts are easier to make crash absorbant, but skids can also be made acceptable. Most skid helos are ancient designs, made before crash absorbtion was considered.

John Eacott
---------------

Great pic John. Now I know why the training captains always say "wait for it, wait for it, NOW!"

By the way, is it true that 76C+'s tend to develop a wrinkle aft of the baggage department after too many rejects? Useful walkaround tip: as you check for tailstrikes, glance along the underside...

Someone really must have had a case of Concorde Envy....but it is supposed to be a drooped snoot isn't it?

Can you imagine the critique by the TRE...."A bit late on the collective pull Hoskins! It should be before the first touchdown....not the second one!":{

Skids vs wheels
 

Nick,

Remember these retractable skids? :D

http://www.helicopterservice.com.au/...20skid%204.jpg

Just want to add one more poit to Nick's:
For mountain work where you have to do a lot of toes landings over edges of stones pointing out of the terrain, it's much better IMHO skids than wheels;)
Buen vuelo

Nick,

One disadvantage to wheels in rocky ground is the ability to knock brakes and sometimes brake lines off the wheels. But in general...much happier on wheels than skids. Took some getting used to when steering the Chinook by the aft gear but having been a fork lift driver during high school it came to me pretty quick. You could whack all sorts of things with the aft blades if you were not thinking while making turns in tight places.

SASless you're quite right on your comment about being aware of aft rotor during tight turns in Chinooks. When the Spanish Army got its first one (reg ET 401) the pilot from BV was moving in one corner of the platform and inadvertedly (of course), hit the corner of a hangar with the aft rotor blades. What happened was that the helicopter lifted from the nose and did half a looping with the aft wheels on the ground. It burnt out to ashes :( but nobody was hurt :O
Don't know if the pilot had to explain something in Philadelphia since BV got another helicopter to replace that one.
Buen vuelo

Brakes should be off when landing following an EOL. That was the technique on the military wheel u/c helis

Matador....

I know some folks that were involved in that escapade....met them at the Agusta factory in Gallarate years ago. Spent many an enjoyable evening on the patio of the Campeggio Jolli on the river with them.:ok: