Bryan Wood
Well Known Member
I'm currently reading Sparky Imeson's "Mountain Flying Bible" and just can't get enough of his little tricks or rules of thumb to quickly figure out information that is very useful. I've been playing around with this one quite a bit and even used it to make up spreadsheets in Excel for flight planning. His rule of thumb that I'm refering to is to quickly calculate how long a flight will take without all of the steps used the way we are taught in groundschool. While this is crude and just a ballpark I have found it to work out within a minute or so on all the examples that I've tried as compared to figuring the old tried and true method. No, it doesn't account for wind, but since all the possabilities are charted in Excel different charts can quickly make comparisons. Here is an example, which you can see works out within a minute using both methods.
Assume a 300nm flight with a cruise speed of 165 knots with a cruise altitude of 7500'. Using a traditional method to get an approximation of time enroute and knowing the typical climb performance of my RV it would take 9 minutes to reach 7500' at a indicated airspeed of 105 knots and would cover 16nm's. With 284 remaining at 165 knots it would take 1 hour and 44 minutes to cover the distance for a total of 1 hour and 53 minutes.
Using Sparky's method it would go like this. Take the total distance of 300nm and the cruise speed of 165 knots for a enroute time of 1 hour and 49 minutes. Now take the cruise altitude and divide it by 2000 (2000 for a constant speed RV, use 1500 for a fixed prop RV, and 1000 for a typical spam can) and add the answer to the 1:49. 7500/2000=3.75 This results in 1 hour and 52.75 minutes compared to the above example of 1 hr. and 53 minutes. Pretty neat isn't it?
Here are a couple of more of his little tricks, only without the explanation. They are really self evident, but also neat. If any of you know any useful little tricks like this please share them. My mind is starving for more of these neat little bits of experience.
More examples:
Do not climb more than 10 minutes for each hour of en route flight time.
In the Northern Hemisphere if you stand with your back to the wind the low pressure will be to your left, and the better weather will be to your right.
Drop the last digit of your groundspeed and you will fly that many miles in 6 minutes.
Regards,
Assume a 300nm flight with a cruise speed of 165 knots with a cruise altitude of 7500'. Using a traditional method to get an approximation of time enroute and knowing the typical climb performance of my RV it would take 9 minutes to reach 7500' at a indicated airspeed of 105 knots and would cover 16nm's. With 284 remaining at 165 knots it would take 1 hour and 44 minutes to cover the distance for a total of 1 hour and 53 minutes.
Using Sparky's method it would go like this. Take the total distance of 300nm and the cruise speed of 165 knots for a enroute time of 1 hour and 49 minutes. Now take the cruise altitude and divide it by 2000 (2000 for a constant speed RV, use 1500 for a fixed prop RV, and 1000 for a typical spam can) and add the answer to the 1:49. 7500/2000=3.75 This results in 1 hour and 52.75 minutes compared to the above example of 1 hr. and 53 minutes. Pretty neat isn't it?
Here are a couple of more of his little tricks, only without the explanation. They are really self evident, but also neat. If any of you know any useful little tricks like this please share them. My mind is starving for more of these neat little bits of experience.
More examples:
Do not climb more than 10 minutes for each hour of en route flight time.
In the Northern Hemisphere if you stand with your back to the wind the low pressure will be to your left, and the better weather will be to your right.
Drop the last digit of your groundspeed and you will fly that many miles in 6 minutes.
Regards,