crash tolerance of aircraft landing gear

[mstachowsky]

I'm wondering if the 50m/s crash tolerance means "50m/s straight down" or just "speed of 50m/s". I'm betting it's the latter, since I've landed at 54-60m/s a few times but was going very slowly down and nothing was wrong. I ask because I'm about to send a refueling tanker SSTO to Laythe and don't want to find out on landing that I can't get an extra 5 m/s out of it. Any thoughts?

MIKE

[nli2work]

it's vertical speed. The speed above the navball is speed relative to the planet surface or orbital velocity. the dial to the right of the ASL altimeter is the ascent/descent speed. 0 is in the middle, level flight.

[Taki117]

nli2work is correct, it is vertical speed, however, while the landing gear might be able to survive that, the rest of your aircraft may not.

[mstachowsky]

Interesting. How do you mean "the rest of the aircraft may not"? Is it possible to land at, say, 49m/s vertical and the rest of the plane blows up? (that would be awkward...)

Does the horizontal speed factor into anything?

[quasarrgames]

First question: Yup. Normally if you're landing on a slightly uneven surface that happens, but it can even happen on the runway too.

[mstachowsky]

Huh, yeah I just tested all of this out. I landed a plane (on the runway...) at 75m/s on the speed indicator but 5m/s ishly on the vertical speed indicator and I was perfectly fine. I have been landing WAY too carefully the WHOLE TIME I've been playing KSP :-P This explains why I always overshoot my landings by a few km by trying to keep my speed indicator under 50. Huh, this will definitely change how I play...Thanks everyone!

[HafCoJoe]

I'm not sure... I've been testing out the plane landing gear as of recently and I built a rover-car that goes just over 100 m/s on Kerbin while sustaining plenty of air and hard landings. See here. I really have no clue what exactly the crash tolerance means.

[nli2work]

landing gears can wobble at higher speeds, resulting in the plane tilting or tipping over, and then you get other, more fragile, parts of the craft hitting the ground,

[Grumman]

I just did some testing as well. Both the wheel and the undercarriage bay have this high crash tolerance, and as long as you don't hit so hard that the wheels clip into the ground, everything else survives. By chaining two undercarriages together, I was able to get enough length to drop a test rocket at ~40 m/s and have it bounce, unharmed.

[Taki117]

Interesting. How do you mean "the rest of the aircraft may not"? Is it possible to land at, say, 49m/s vertical and the rest of the plane blows up? (that would be awkward...)

Does the horizontal speed factor into anything?

Meaning if you hit the ground hard enough the landing gear will compress and the lower part of your rocket will hit the ground resulting in an explosion.

[SpacedCowboy]

There is absolutely nothing wrong with "landing WAY too carefully"!

[Kasuha]

I'm not sure... I've been testing out the plane landing gear as of recently and I built a rover-car that goes just over 100 m/s on Kerbin while sustaining plenty of air and hard landings. See here. I really have no clue what exactly the crash tolerance means.

The speed at which you can go on that gear has nothing to do with impact resistance. I was traveling close to 1300 m/s on that gear on Minmus without it breaking.

Aircraft landing gear is special in many ways. It has no weight, it has high resistance to almost everything, and it provides light without consuming electricity. But it's very fun to play with.

[mstachowsky]

There is when you overshoot your landing site by 5km with a big fuel tanker, especially on non-flat ground where you aren't sure if there will BE a landing site in 5km :-P

[Heagar]

If you are worried about a landing on Lathe - with it's small continents with uneven terrain - try something unusual.

When the landscape of Kerbin was newly modeled (steep terrain), i wanted to build an SAR-plane capable to land on the smallest possible places - even at high altitudes. The answer for not chrashing every time into the next hilly part of the terrain was to add parachutes to the craft. Not for descending, but for braking!

You simply extend the landing gear, enable the brakes and try to achieve an altitude slightly above the ground at you landing-spot. Your airspeed should be below 40 m/s. Then release your parachutes - witch should be done preferably with an actiongroup.

In my case (on kerbin) the plane stood still after 20 m without any damage.

@Kasuha: It haven't any weight that counts into the craft-mass when launching. But in the SPH it has an weight (0.5 t) and an influence regarding the CoW, especially for small planes. I wonder if it's drag have an impact on the plane in flight ...

[mstachowsky]

I've experimented using parachutes for landing before, it was pretty good for sure. I've gotten fairly decent at getting my landings working now, and mainly I land on large, flat areas. I think, though, that with my newfound understanding for the strength of the landing gear, I can hit some fairly steep slopes and still be OK.

MIKE

[linkxsc]

Interesting. How do you mean "the rest of the aircraft may not"? Is it possible to land at, say, 49m/s vertical and the rest of the plane blows up? (that would be awkward...)

Does the horizontal speed factor into anything?

Horizontal speed doesnt matter to your landing gear. Only vertical (because its measuring the relative force that the gear are taking when they hit remember 1 thing though. The 50m/s is a nominal term. Heavy aircraft can break them off when landing at lower speeds.

Also on the "your plane may explode". Sometimes if you hit hard. Linkage between parts will break (fixed with struts). Other cases like a lot of aircraft with anhedral/lower mount wings. The wings can smack off the ground in a hard landing because the gear compressed. This was especially problematic for my early X-wing designs which often hit a little hard before i started adding a slight canard to the leading edges of the wings.