Lancair888

Using anything other then spring air is foolish and you should be ashamed.

Air up/down rectracts are the dumbest idea EVER, I have seen every brand fail, to the detriment of every model.
They fail, the air fails, leaks, valve fails, ect. I would NEVER EVER trust ANY of my models to pneumatic retracts, EVER.

Lets recap....

Mechanical retracts, 99.9% success rate, inspect for bent gear and mantain smooth operation, make sure you have bec so u don't overload servo and lose flight control.
These will almost never fail, downside they don't make them for large models, wish they would.
- Not really scale opperation at all. Not available in large models.
+ Works 99.9% of the time, reliable.

Pneumatic (air up/down) retracts. Horrible foolish junk, lets trust our $100-$10,000 model on some tiny little air cylinder and hose, if you get a leak you have NO wheels if they get stuck half in or out, your screwed. BAD, BAD, BAD, only fools and noobs would trust in this garbage, even real planes would never use this, so why would you trust it in your model? These have a 50/50 success rate at best when rediculous attention and maintenance are used on them.
+ Can perform totaly scale
- High failure rate, no backup, if they fail ur screwed

Spring air (air up, spring down) When you have an air failure these retracts automatically deploy, you ALWAYS have wheels using this type, they are 99.9% successful.
What more can u say? they work always, this is the only logical choice other then mechanical, pneumatic should not even be sold, or allowed there dangerous.
+ Always come down on failure, no more belly landings. Can raise scale. Failure means your wheels came down, telling you they failed, and giving you wheels 99.9% of the time.
- Can not lower scale, they come down fast at the same time.

Choose wisely, scale is nothing when your model is busted or damaged. lose 1 scale detail to maintain your models integrity for life.