how do you work under a MH with air bags?

WARNING,
My neighbor was killed about 30 years ago when his air brakes leaked down & caused his 40' Bluebird to roll forward off of wood ramps. He was in the worst place possible when it rolled forward. He was laying down working under the low-slung steel generator "box."
Wished I could give a solution to op's original question, however, just had hand surgery!

I do a couple of things.

Drive up on some home made ramps...~3.0"
Drop the jacks
Attach the hose from my compressor set at 120 psi.

With the 3" blocks, I'm safe even if the air drops which is unlikely since it's still supported by the jacks and the air compressor keeps the air up unless I do something incredibly stupid (always a possibility)

Most will have automatic safety jacks, often called leveling jacks.

My leveling jacks will raise the front axel off the ground, so I use it as a jack, and then block as required to hold the coach while I do what is necessary.

The back axel jacks will not raise it off the ground, so I simply raise it as far as it will, and place blocking to insure I don't cause it to release the air and lower its self. my blocking is 12"X12"X2' wooden blocks

When I need to go down under, I use 6x6 blocking. each aprox. 18"long. I set 4 pcs. one way with another 4 pcs layed cross wise on top with another 2 2x8s running perpendicular on top of the 6x6s.
then I use assorted blocking to make a ramp to drive onto the 6x6 blocking.
After the wheels are on the 6x6s, I place more blocking under the hydraulic levelers.
Next I dropped the air pressure, making sure that the bags are fully deflated. I then check that all blocking under the tires and jacks is square and true.
I check the jacks and their blocking.
At that point I crawl under to perform my PMs.
One thing to remember that the air rides/air brake coaches only have spring air brakes on the rear wheels and not on the front. So always make sure that the front wheels are properly blocked if you intend to lift rear axle or remove rear wheels.
Last note when that coach is sitting up on blocks I make sure all wheels and jacks have solid blocking (no cinder blocks) under points of support.

Just make sure that the "blobks" that you use are NOT concrete blocks. I prefer heavy duty jack stands, rated to hold the axle weight of the vehicle, as a minimum and make sure that the base of the jack stands is on a surface that can support the vehicle weight. Dirt or gravel is not a good surface to support a jack stand. The jack stand should be installed under the frame of the coach, not a body panel.

You have three options. One is to drive it over a pit, but few people have a pit in their back workshop. A second is to drive it up on ramps. What I do, and most people do and what is recommended by all, is jack it up and put blocks under the chassis hard points. Never get under an air suspension vehicle without blocks, basically. What you will find is that for much service you actually are better off taking a wheel or two off, so you need to jack it up anyway.

Brian

I'm new to this too, however I have learned that with Foretravels a steel 2x2 x 1/4 inch thick post at a prescribed length is placed in a recommended (by manufacturer)position in all four corners which takes the place of fully inflated air bags. This is the recommended safe way to elevate your Foretravel if your going to get under it.