Tankers don't always carry full loads

I want to briefly mention something that I will spend more time writing about later after I have had a chance to do some research as well as talking to my aviator friends. That is, more often than not, tankers and helos will not carry a full load of retardant or water in their tanks due to aeronautical concerns. So, when the reports are saying that the Martin Mars can carry 7,200 gallons of water/gel mixture or that the Evergreen 747 supertanker can carry 20,500 gallons of retardant, they will carry these loads under "ideal" circumstances. The word "ideal" may be a misnomer, but it will have to suffice for now.

So, the Martin Mars was, as Bill Gabbert pointed out the other day, was carrying a smaller load of water (about 4,600 to 5,500 gallons). Chances are the Evergreen 747 supertanker was carrying a smaller load of retardant. Those of you who are aviators, or firefighters more familiar with aeronautics than I will know that one of the main reasons that tankers (and I assume helos) carry a lower load is because of something called density altitude. I will be writing some articles later about density altitude. I had begun discussions with some of my fire aviator friends several weeks ago about points such as density altitude and retardant coverage levels. I am beginning to revisit these issues.

One final point, while I am on the subject. When the Fox newscasters were covering the other day about the Evergreen 747 supertanker's retardant drops, one of them said that the supertanker could lay down a retardant line 3 miles long. This was also under "ideal" conditions and when the load is dropped in one run. I will add here that they were reading from specifications and other data on the supertanker, as they should. Having read specs myself, what I have to remember is to read words like "maximum" or the data sheet might say something like "the supertanker can drop a retardant line up to three miles long." Point being that I have to remember to think about these words as I listen to newscasts or read articles online.

Returning back to retardant line laid by the Evergreen 747 supertanker, the supertanker split the load into two runs, as all tankers are able to do. Likewise, at full capacity and under ideal conditions, the Martin Mars can cover 4 acres with its water/gel mix. If I understand things correctly, each water/gel load dropped by the Martin Mars covered less than 4 acres. Again, in later articles, I will try to write more about this issue.

I will also be writing about other aerodynamic issues relating to retardant and water drops. In some sense this planned series of articles will be a continuation of the short series of articles I wrote several weeks ago on wing stalls as relates to retardant drops. I won't link to this here, but if you look at the labels on the lower left side of this page, you will see a label that says "aerodynamics." If you click on that label you will get all my posts on aerodynamics to date, including posts on wing stalls.

Look for this series down the road a bit.