What is the approximate rate of descent needed to maintain the electronic glide slope at 105 knots ground speed?

To determine the approximate rate of descent required to maintain the electronic glide slope while traveling at a ground speed of 105 knots, it's important to apply the standard glide slope calculation, which is based on the concept that a 3-degree glide slope requires a descent rate of approximately 300 feet per nautical mile.

At 105 knots, the aircraft covers about 1.75 nautical miles per minute (since there are 60 minutes in an hour). To find the necessary descent rate, you can multiply the glide slope rate by the distance covered in a minute:

1. Calculate the distance covered in feet per minute:

• 105 knots = 105 nautical miles per hour

• 1 nautical mile = 6076 feet, so:

• 105 nautical miles/hour = ( 105 \times 6076 ) feet/hour

• This equals approximately 638,000 feet/hour, which is about 10,633 feet/minute.

2. Using the standard glide slope formula for a 3-degree descent:

• For even Cessna aircraft, a 3-degree angle gives a rate of descent of about 5.3 times the ground speed in knots.

• Thus, at 105 knots: