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Flightinfo.com, LLC "Rules Of Thumb" page is full of ideas from experienced pilots. These "Rules Of Thumb" cover the basics, from when to start your descent, to power setting in turbo-props. Gleaned from seasoned pilots, this practical information will assist you in maintaining good piloting procedures and skills. This page is a great place to find helpful suggestions. In addition, any tricks of the trade that you have learned in your years of flying would be a welcome addition to our "Rules Of Thumb".

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DESCENT:

#1 - 3 degree Glide Scope

Divide groundspeed by 2 then add a "0"

90kts/2=45, then add a 0...

45(0)= 450fpm

#2 - 3 Degree Glide Slope

To maintain a 3 degree glideslope (eg: ILS) multiply the groundspeed you are achieving by 5. The resulting number is the rate of descent to fly.

Ex. Groundspeed = 110 Kts x 5 = 550fpm rate of descent to maintain 3 degree glideslope.

#3 - 3 degree glide slope

With glideslope out on an ILS approach with DME, multiply the distance to go by 300. That should give you the height in feet you should be above the threshold.

4nms to the threshold. Multiply by 300 = 1200ft

#4 - 3 Degree Glide Slope Descent Rate

Add a zero to your indicated speed, divide by two. This should keep you stabilized on the approach.

EX: 150 knots on the GS. 150(0) / 2 = 750fpm descent. 120(0) / 2 =600fpm descent, etc.

#5 - 3 degree glidslope

Take your AGL height and divide it by three hundred. This is the distance from the threshold you need to start your three degree glidepath.

600agl/300=2 nm.

#6 - 3 times the altitude, plus ten

To estimate the point from the field to begin your descent, multiply your altitude (whole numbers)by three and add ten.

To descend from FL 350: 3 x 35 = 105 + 10 = 115 miles out

#7 - ANOTHER DME MAP TIP (VDP)

Multipy the Height Above Touchdown (HAT) for the approach minimums to be used by 3, then divide by 1000 (or just move the decimal place over three places). To limit mathmatical gymnastics, round up the HAT in 50 ft intervals (HAT 327 to 350, 365 to 400, etc.) As in tip 24, add or subtract the distance to the DME MAP to obtain a 3 degree GS.

VOR/DME Approach with the FAF over the VOR and MAP @ 4.5 DME. HAT (always AGL)is 300 ft. 300 X 3 = 900 or 0.9 DME - Start descent @ 3.6 DME for a 3 degree GS.

#8 - Approach To Landing

When making a VFR approach to landing, intercept the extended centerline of the runway and keep the (rwy) numbers about two inches above the nose of the acft (Cat. I)as visable from the cockpit. This will also determine your throttle setting for best rate of decent.

Once on final should the rwy drop below the cowling, reduce throttle until it repositions to the desured height then add power to maintain stability.

#9 - Approximate Vertical Speed FPM

For descent speeds of M.74 - M.80 upto 320 KIAS the following vertical speeds are necessary to make good thefollowing descent schedules:
1500 fpm for a 4-1 descent
2500 fpm for a 3-1 descent
3500 fpm for a 2-1 descent

to loose 10,000 feet at 4-1 would take 40 miles and 1500 fpm.
to loose 10,000 feet at 3-1 would take 30 miles and 2500 fpm
to loose 10,000 feet at 2-1 would take 20 miles at 3500 fpm
to loose 6,000 feet at 3-1 would take 18 miles at 2500 fpm. etc.

#10 - Correct time to Lower Gear

Preferably before coming into contact with the runway surface.

EX: 1000 TPA, you descend on base, turn final, cross threshold and land with your gear still in the up position.

#11 - Correction

# 7, listed above, is a little off. Should be gnd spd, not IAS, and should by mult by 10, not 100.

#12 - Distance To Decend

1. Take your altitude and multiply it by 3. That equals your distance in miles to begin your descent.

2. Now take half your ground speed. This is your rate of descent in hundreds of feet.

Ex.If you are flying at 12000ft at a ground speed of 150kts and you need to descend to 2000ft, the difference is 10000ft. Multiply 10*3=30 miles out you must begin your descent. Half your ground speed is 75, add a zero, and 750 ft per minute is your rate of descent.

#13 - Easy Vref Calc for CE-550

Dont have a quick cheat list for ref speeds for the ce-550? Take you fuel remaining per side above 500lbs and add 1 knot to 90 for each 100lbs

Fuel remaining = 1000lbs per side
1000-500 = 500lbs = 5 knots
90 kt + 5 kt = Vref 95

#14 - EXACT rate of descent for a certain distance

Altitude in FL divided by Distance in Miles gives Flight Path Angle (modern Airbusses have a FPA vertical mode)
To convert to Feet Per Minute, multiply FPA by ground speed times 1,7. Also works for climbs

"Leaving FL310 descending FL230 to reach within 40 Miles" Ground speed 400 kts.
310-230=80 levels
80/40= 2 degrees FPA
2 * 1,7 * 400kts = approx. 1400 FPM

#15 - Glide Ratio

100 ft/min is approximately 1 knot. So to figure your glide ratio: ground speed divided by VSI/100 (just drop the zeros).

Ground speed = 100kts.
VSI shows 500 ft/min down
Drop the zeros = 5 kts
100/5 = 20:1 glide ratio

#16 - Icing/Turbulance decent

This formula works for turbo prop pilots wanting to stay out of icing and turbulance. It gives you a way to meet a crossing restriction and stay high as long as possible.

Take the difference in altitude and multiply times three. This will give you the distance from your crossing restriction to begin descent or "top of descent."

Now multiply your ground speed time six. This will give you your rate of descent in feet per minute.

You are level at FL210. ATC tells you to cross XYZ at 9000 feet. You are 85 NM from XYZ with a ground speed of 300 knots.

21000-9000 = 12000 (drop the zeroes and use 12) X 3 = 36nm

300 X 6 = 1800 or 1800 feet per minute

36 miles from XYZ you must start down at 1800 fpm or greater to meet the restriction.

It works!

#17 - JET RULE FOR DISTANCES

1. A jet takes 10 miles to loose 4000 feet of altitude still wind.

2. A jet takes 10 miles to slow from cruise speed (around 320 kts) to a clean speed (around 200 kts).

If you have a tail wind then just add 5 or ten miles and vice versa - really does work!!

eg. Aircraft at 30,000 ft to do down to 10,000 ft and slow to holding speed. Tail wind of 30 kts.

So, 4000' is 10 miles, so 20,000' to loose is 50 miles. to slow down is another 10 miles. Total is 60 miles. As there is a tailwind add a bit more, so answer is about 70 miles! REALLY WORKS!!!!

#18 - LCGUMPS

L-Landing light
C-Carb heat on
G-Gas fullest tank
U-Undercarriage
M-Mixture set
P-Power set
S-Safety check

Works better and anytime including night.

#19 - mistake

ROT #3 for a descent is worded incorrectly. It states that to determine your descent rate, you take half of your groundspeed, and that gives you your descent in hundreds of feet per minute, when in fact, it gives you your descent rate in tens of feet per minute (you add one zero. hundreds would mean adding two zeroes)

#20 - Mx a 3 degree glide slope

Ground spd divided by 2 and add a "0"

120k=Grd spd...120/2=60 and add the zero. 600fpm is required to mx a 3 degree glide slope.

#21 - Precision or Non-Precision Glide Descent:

Divide your IAS by 2 & Multiply by 100 to get 3* FPM descent.

EX: IAS 160Kts/2= 80 X 100 = 800FPM Descent to keep a 3* GS.

#22 - Rate of Descent FPM from cruise (no wind)

Mach x descent gradient. Idle power.

.8 x 3 degrees = 2400 FPM

#23 - The distance to descend

The distance to descend at 500 ft per minute. Equals 2 times the ground speed in miles-per-minute times the altitude to lose in thousands of feet.

Ex.If ground speed in the descent is 155kts/180mph(3 miles-per-minute) and you must descend 8000ft, you must begin you descent 48 miles from the point at which you must be at the lower altitude. 2 times your 3 miles per minute ground speed equals 6 times 8 (your altitude to be lost in thousands) equals 48 miles.

#24 - THREE G'S

So you don't forget anything in a complex airplane, either in an instrument approach or in the traffic pattern. This is to be done at the FAF or when turning base.
Gear down
Go down
GUMP check

#25 - Time to See

Provides a deadline on a timed approach at which a normal 3° descent to the landing surface can be commenced when the MAP is at the runway

MDA(AGL) multiplied by 10%.
Subtract that figure from MAP timing to arrive at point for a normal descent at 120kt

MDA is 400 ft
Timing to MAP is 1:20 secs
10% of 400 = 40
Runway Surface must be in sight 40 secs after timing commences to decend normally to runway at 120

#26 - TOD and ROD

The rate of descent calculation stated in number 12 actually is giving a rate of descent for 300'/nm which works for the approach but not for 3 NM/1000' (=333'/nm) during enroute descent. The required rate of descent is greater than G/S divided by 2 times 10. Granted at low goundpseeds the difference isn't much.

E.G. 180 knots = 3nm/min. Therefore the ROD required at 180 knots to loose 1000' every 3 miles is 1000'/min.

360 knots requires 2000'/min. 270 knots = 1500/min.

#27 - Top of Descent

Top of Descent. For descent speeds of M.74 - M.80 multiply the # of feet to loose x 3 divided by 1,000'

FL350 to 10,000' = 25,000' to loose
25 x 3 = 75 miles

#28 - When and Rate

Alt to loose x 3 devided by 1000 will give you a distance from a known location to start your decent. Groundspeed/2*10 will give you your required rate of decent for a 3degree glide slope.

FL350 @300KTS. 35000 X 3 = 105000 / 1000 = 105nm from your destantion you must start your decent. 300KTS / 2 = 150 x 10 = 1500 FPM is your desired rate of decent

#29 - When to Begin Your Descent

Start descent when time to airport equals altitude to lose for 1000 ft/min descent

10000 feet to lose, start descent 10 minutes out at 1000 ft/min

#30 - When to begin your descent from MDA (DME MAP)

Divide MDA (ft AGL) by 300 then add or subtract as necessary to find the DME point to start the descent. If final approach course is going away from the VOR, subtract from the DME MAP, if it is going towards the VOR, then add.

VOR/DME Approach with the FAF over the VOR and MAP @ 4.5 DME. MDA is 400 ft AGL (400/300=1.3) Start descent @ 3.2 DME for 3 degree GS.

#31 - When to begin your descent?

Divide the difference between Cruise Altitude and Descent Altitude by the Rate of Descent. That value is your Time to descend. Multiply this by your Groundspeed in Cruise and divide the result by 60. The result is the DME prior to which you need to begin your descent

EX: FL360 to 6000' = 30,000' /1500'per minute = 20 minutes.
Now, (20x420 Knots G/S)/60 = 140 nm from the desired point.
Try it, it really works!!!

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