Check that tire pressure!

Now that temperatures are dropping and affecting tire pressures, I thought I'd talk a little bit about that. 

I had a good opportunity to be reminded of how important it is to keep regular tabs on how the air pressure is doing just the other day.  Luke and I were attempting to push a plane around on our ramp and had a really hard time of it.  After verifying it wasn't the brakes, I got down and had a close look at the mains.  Wow!  They were very low. 

As we all know, the wheel fairings are pretty tight and the wheels can be hard to see.  This tends to make many Cirrus pilots get out of the habit of having a close look at the wheels.  Really it isn't so hard to see them if you get down close to the pavement and look in from a foot or two.  This view will tell you what you need to know about the tire pressure and it's also a great time to check those white stickers on your brakes.  If I had a dollar for each time I've found those stickers dark gray or black on an owner's plane when I do my preflight on it, I'd at least be able to fill my car with gas.  That subject is a blog post for another day...

Let's say you haven't been doing that.  First - start doing it.  I'll tell you a little about how to train your eye below.  But say you're taxiing along - can you tell if your tire pressure is low?  You bet.  Every Cirrus pilot should be aware of how much energy is being used to taxi.  If you're rolling on a flat paved surface without much of a slope, you should be able to keep the plane rolling without much more than 1,000 to 1,100 RPM.  Breakaway thrust is always a little more just to get the plane rolling, so don't worry if it takes 1,200 or 1,300 to start taxiing... but once it's moving, throttle back.  If the plane slows down quite a bit then you've got an issue.

As a preventative measure, make sure your service center is checking your tire pressure at every oil change, or just do it yourself.  Keep in mind that you have to ask the mechanics for this, they won't always just do it.  Since most pilots only do a couple of oil changes a year, this interval might not always catch the problem when pressure starts to get low but it's a good way to help with prevention. 

Many clients ask me how to tell if the pressure is too low by looking at it.  That's a tough thing to describe with just words, but you can easily find out with a simple experiment.  Make sure you've parked near where the air in your tires can be filled (many portable tanks won't do this too well) and, using a pressure gage, release the pressure in one of the main gear down to about 30 or 25 psi.  Now fill the pressure back up to 62psi in SR22s and 53psi in SR20s.  You should be able to notice the difference quickly, a very significant bulge will be evident when the pressure is low.

Another method which some prefer is to cut a block of wood which fits just under a fairing when the tires are properly inflated.  If pressure drops, the block will not fit as well.  This method requiers a little more work and is succeptible to tread-wear, but it works. 

Regardless of the method, make sure you're keeping track of your tire pressure.  Low pressure can have all kinds of bad side effects from excessive tread wear to loss of controll on landing.  It's a really easy thing to maintain too. 

Safe flying!

John Fiscus

Chief Pilot

The Flight Academy

www.theflightacademy.com