Do all bolts need washers? Usually, only two factors are involved. Is the hole oversized, and is the bolt configured to work without the washer?
Turn the bolt over and look at the underside.
The first one on the left is simply flat. Number two is an AN bolt and has an area that acts as a washer. The third one has an enlarged surface, and the fourth has a separate, permanently attached washer. Only the first one must have a washer. The second one, does not require one, the third one has a washer built in, and that last one has a permanently attached washer.
Only the second one should be used on aircraft, though, as it’s the only one whose manufacture is fully pedigreed.
AC 43-13 section 7 allows you to skip the use of washer under an AN bolt. But a few AD's do, at times, require washers under both the bolt and the nut.
If you’d like to read further on this topic and don’t have a copy of AC 43-13 beside your bed, you can download it HERE.
Yes, you do, if you’re going to fly safely. And while there are a lot of websites out there that give you all the information you need, some of them are buried in advertising or not reliably updated.
One that suffers neither of these flaws comes from our own gummint. Yes, the National Oceanographic and Atmospheric Administration have a wonderfully complete and up to date plethora of pages on the subject.
When you’re done here, browse over to http://www.weather.gov/forecasts/graphical/sectors/ and click on your area of interest on the map. Down the left you’ll find a matrix of times and weather parameters. You can easily kill an hour just watching the predicted changes. This series will become a favorite if you're headed out for lunch in that it shows ground conditions. If you're going further, you'll also find links to pages specifically for aviation. As for those other sites? This is where they get their data.
NOAA needs to work on the name though; "Administration" at the end of it implies control of said oceans and atmosphere and that’s a long way off.
KITPLANES readers will recall a recent article about Dan Parker and his High Flyer (January 2008 issue). He is in the process of designing and building an aircraft that he hopes will set a new world record of 31,051 feet for aircraft with a takeoff weight of less than 300kg.
Dan has informed us that he's made that milestone of attaching the wings and is hoping to fly it this Spring from an airport in Northern California. The requirement is that he has to take off with no external assistance such as a tow, and land with all the parts he had on take off, meaning he can’t drop the wheels or throw out oxygen bottles.
We’ll be watching this closely and reporting the flight. To see details of the aircraft go to Dan's website.