Why are...

XvX · August 30, 2007

..skids called skids? I mean, you're not supposed to skid on the ground with them, right? Hmmmm.

Eric Hunt · August 30, 2007

Wrong.

Of course you can skid on them - running landings, running takeoffs, hydraulic failures, and just for fun.

They provide a reasonably stable platform for landing on uneven or soft ground, somewhere for a photographer or winchman to rest his feet, a place to tie your fishing rod, and a place to tape some smoke canisters for a fly-by.

Gomer Pylot · August 30, 2007

IME they're a rather UNstable platform for landing on uneven ground. The most stable configuration you can come up with is a tripod, and wheels form a good one. The main reason for the use of skids is money - they're cheap to build and maintain, compared with wheels, and especially retractable ones.

BillyBob · August 31, 2007

IME they're a rather UNstable platform for landing on uneven ground. The most stable configuration you can come up with is a tripod, and wheels form a good one. The main reason for the use of skids is money - they're cheap to build and maintain, compared with wheels, and especially retractable ones.

Gomer,

Is this why the Army went all wheels after the 58 series.

Except the new UH-72 I guess.

Any Insight?

Gomer Pylot · August 31, 2007

Nope. When I got out we were still flying UH1s. But large tires are a much better solution to landing in rough terrain than skids. Or even small tires. Tires also give much more traction on slick surfaces. Landing an S76 on a sloping wet deck, like a tanker, is much safer than landing a 412, an aircraft of similar size and weight, but with skids. With skids you don't really get much surface contact, just the high points of the shoes, sometimes less. Three rubber tires are very stable almost anywhere. I've had lots of aircraft on skids spin with me, but never one on wheels. The tailwheel on the Blackhawk gives even more stability because of the wide distance between the points of contact.

james28 · August 31, 2007

what if you are on a soggy or mushy surface? which is better?

HelliBoy · August 31, 2007

The main reason for the use of skids is money

I'd change money to wieght- skids are lighter than wheeled assemblies, especially retractable ones, and have less drag than non retracts. They also provide a much larger surface area for ground contact on soft surfaces. Skids offer more utility in my opinion, wheels might be better for landing on smooth, hard surfaces, but smooth hard surfaces are for beauty queens I'll make an exception for some of the more ruggedized military models..blackhawks and chinooks

Gomer Pylot · August 31, 2007

It may be a tossup, and it depends on the tires, I think. I haven't spent a lot of time on those, but if the skids can sink down enough to deploy more surface area, they might win. But if they do sink, look out. Dynamic rollover isn't far behind. Same thing with wheels, though. You need to be very careful if you land on something like that, and come up to a hover very, very slowly and steadily.

Hovergirl · August 31, 2007

Isn't ground resonance more likely with wheels, or is my memory failing me on this one....

Gomer Pylot · August 31, 2007

Not necessarily. Improperly inflated struts can be induced to ground resonance by improperly balanced rotor systems, but every instance of incipient ground resonance I've ever had was with skids. The Hughes 269/TH55/Schweitzer 300 is susceptible to it because of the articulated head and oleo struts, and the AS350 will go into it in a heartbeat. I've had several try it, most stopped by lifting to a hover when it started. One started after I had gone to idle, and I rode that one out, killing the engine and engaging the rotor brake, and it only turned about 45 degrees on the pad before it stopped. I've never had a wheeled helicopter try to go into it, but I do keep an eye on the struts for proper inflation.

XvX · September 1, 2007

Hmmm, rolling takeoff with skids? The only Helo that I can think of the needs a running takeoff is the fully-loaded Mi-24, and that has wheels.

Gomer Pylot · September 1, 2007

The UH1 often needed a 'rolling takeoff'. Get it light on the skids, start moving forward, and eventually get going fast enough to fly. I've done lots of those. I've also done them in the S76, on wheels, mostly for practice, but it's a useful technique under some circumstances.

I missed Helliboy's post earlier. I don't agree that skids have less drag than wheels. There's a lot more surface area on skids than wheels. Skids may be marginally lighter than fixed wheels, but not usually. They are probably a little lighter than retractable gears, but mainly they're cheaper to buy and cheaper to maintain, being just metal tubes. They can be changed easily and quickly.

Edited September 1, 2007 by Gomer Pylot

Skids Up · September 2, 2007

The UH1 often needed a 'rolling takeoff'.

Was the UH1 underpowered or overweight? Would think that takeoff places would be pretty limited if you had to drag it off, thinking strictly of some of the bush spots we work out of....

...not a slag, just curious.

Linc · September 2, 2007

I thought ground resonance was in three-bladed systems (Alouette, Hughes 269, Chinook, etc.)?

Gomer Pylot · September 2, 2007

You can get ground resonance in any fully-articulated rotor system, whether there are three or five blades. Three blades is the most common configuration.

The UH1 wasn't necessarily underpowered, at least in the later versions, like the H model, but get it at altitude, very hot, and way, way overloaded, and you do what you have to do. In a hot LZ, you don't stop to weigh every troop that gets on board, you just load up and get the hell out the best way you can. Even loading for a mission, you take the troops they give you and get off with the formation. Things may have changed over the past 30 years, but I sort of doubt it.