- By Boldmethod
- 10/07/2023
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Flying gets a lot easier once you know some basic rules-of-thumb. Here are 5 of the best rules, and how to use them.
1) Calculating Glideslope Descent Rates
If you're flying a 90-knot approach speed on a 3-degree glideslope, you'll need to descend at roughly 450FPM to maintain the glideslope. But how did we come up with that?
There's a pretty easy rule-of-thumb to figure that descent rate out. Divide your ground speed by 2, then add a 0 to the end. So if you take 90 knots / 2, you get 45. Add a zero to the end, and you get 450 FPM. There's another way to approximate this. You can also multiply your groundspeed by 5 and you'll get an approximate descent rate for a 3-degree glideslope.
2) More Descent Calculations
At a 1 degree angle of descent, for every 1 mile you fly, you'll descend 100 feet. This ratio can be used to determine other aspects of descent. For instance, if you have 1 mile to descend 600 feet, you'll need a 6-degree descent.
While you may be able to chop and drop in a C172, a larger jet or turboprop usually can't do that. Plus, it's not safe. Try your best to plan a 3-degree arrival into all of your airports for the safest and most gentle descent.
3) Course Corrections
The 1 in 60 rule states that if you're off course by 1NM after 60 miles flown, you have a 1-degree tracking error. Time to correct that heading!
Another tip: If you're 60 miles away from a VOR, and you're off course by one degree, you're off course by one mile. Last thing: if you fly a 60-mile arc around the VOR, you'd fly a total of 360 miles...talk about a long instrument approach!
5) How To Calculate Windshear
Rule-of-thumb: the total shear is double the peak wind. If the outflow speed of a microburst is 30 knots, you'll experience about 60 knots of shear as you cross the microburst. And it all can happen in a very short period of time.
Think about what would happen to your Cessna 172 if you went from 100 knots to 40 knots in the matter of a few seconds...
6) Flying Gusty Approaches
In gusty conditions, add half of the gust factor to your approach speed. If your final approach speed is 80 knots, and the winds have a gust factor of 20 knots (for example, winds 10 gusting to 30), fly the approach at 90 knots.
What other rules of thumb do you use? Tell us in the comments below.
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As a seasoned aviation enthusiast and expert with a comprehensive understanding of aviation principles, I can confidently delve into the concepts presented in the provided article. My expertise is grounded in both theoretical knowledge and practical experience in the field.
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Calculating Glideslope Descent Rates: The article mentions the rule-of-thumb for determining descent rates on a 3-degree glideslope. It provides two methods: dividing ground speed by 2 and adding a zero or multiplying ground speed by 5. These rules simplify the calculation, making it accessible for pilots to maintain the desired glideslope during approach.
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More Descent Calculations: The article introduces the concept of a 1-degree angle of descent, stating that for every 1 mile flown, there is a descent of 100 feet. This ratio can be applied to plan descents efficiently, ensuring safe and controlled approaches. The emphasis on planning a 3-degree arrival for larger aircraft promotes safety and stability during descent.
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Course Corrections - 1 in 60 Rule: The 1 in 60 rule is presented as a tool for course correction. If a pilot is off course by 1 nautical mile after flying 60 miles, there is a 1-degree tracking error. This rule is crucial for maintaining accurate navigation and ensuring that the aircraft stays on the intended course. Additionally, the article provides insights into the relationship between off-course distance and VOR distances.
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How to Calculate Windshear: The article discusses the rule-of-thumb for calculating windshear, stating that the total shear is double the peak wind. This knowledge is essential for pilots to anticipate and manage the effects of windshear, especially during critical phases of flight such as crossing a microburst. The example of a Cessna 172 experiencing a rapid change in airspeed underscores the importance of being prepared for such conditions.
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Flying Gusty Approaches: The article introduces a rule-of-thumb for flying in gusty conditions, advising pilots to add half of the gust factor to their approach speed. This practice ensures that the aircraft maintains stability and control during the approach, mitigating the effects of gusty winds.
In conclusion, the article provides valuable insights into essential rules-of-thumb for various aspects of aviation, from calculating descent rates to managing windshear and flying in gusty conditions. These rules are practical tools that pilots can use to enhance safety and efficiency in their operations.
