Use of Performance Charts Flashcards
What altitude should you be using when looking at performance charts?
Pressure Altitude
How do you find Pressure Altitude?
- Subtract the current altimeter setting from 29.92
- Multiply that answer by 1000
If the number is positive, add it to your elevation. If it is negative, subtract it.
Finding the crosswind and headwind components (graph)
How do you interpolate what the ground roll will be at 17oC and an elevation of 1000ft?
Performance Chart Ground Roll:
10oC is 765ft
20oC is 825ft
1) Take the difference between distances. 825-765=60
2) Take the difference between temps. 20-10=10
3) Take the difference between the lower temperature value in the chart and the one you are given. 7
4) Turn that into a percentage. 7/10=0.7 (70%)
5) 70% of 60 is 42
6) Add 42 to the takeoff distance at 10oC. 765+42=807ft
How do you interpolate to find the ground roll at 1300ft elevation and 10oC?
Performance Chart Ground Roll:
1000ft & 10oC: 765ft
2000ft & 10oC: 840
1) Take the difference between ground rolls. 849-765=75
2) Take the difference between elevations. 2000-1000=1000
3) Find the difference between the lower value given in the chart and the one you want. 300
4) Find the percentage of that number. 1300/300=0.3
5) Multiply by the difference between takeoffrolls you found earlier. 75x0.3=22.5
6) Add 22.5 to the takeoff roll at 1000ft elevation. 765+22.5=787.5
When adding distance to ground rolls for grass/wet/snowy runways, do you also increase the distance it takes to clear a 50ft obstacle?
No. Runway conditions only affect the ground roll.
What is important to remember about altitude and temperature when using Cruise Performance Charts?
Where it gives temperature columns, you need to use the temperature at the altitude you’ll be flying at not the temperature on the ground
Remember that we lose 2oC for every thousand feet we go up
What does an Endurance Chart look like and what is it for?
How long you can stay in the air given the cruising altitude you choose and the BHP%
What does a Range Chart look like and what is it for and why should it be used with caution?
Range Charts are based on zero wind conditions which is never going to happen. So you will almosty always fall short of what the chart says.
What does a Climb Performance Chart looks like and what is a common mistake students make when using it?
You must take the final altitude you are climbing to and subtract the elevation of the airport as well as all the time, fuel, and distance values.
Example: If you are climbing to 6000ft and taking off from an airport with an elevation of 2000ft then from the chart below we would say it’s going to take us 7 minutes, 1.4 gallons, 10NM
What illusions will an upslope and downslope runway cause?
- A downslope runway can cause the illusion of being too low on approach. The pilot will often compensate by coming in too high
- An upslope runway will give the illusion of being too high on approach, causing the pilot to come in too low
What does CRFI and RSC stand for?
Canadian Runway Friction Index
Runway Surface Condition
What does this NOTAM tell us and how do we use if it regards to the CRFI?
CYWG RSC 18/36 COVERED 1 INS LIGHT SNOW 0401190630Z
YWG Runway Surface Condition (RSC) report:
- Runway 18/36 covered in 1 inch of light snow
- Dated 2004, Jan 19 at 0630 Zulu
Take this info to the CRFI chart in the CFS and figure out how slippery the runway is.
What is the value assigned to a perfect (clear, dry) runway and a terrible (covered in ice/slush) one?
1.0 is perfect
0.8 is almost perfect
0.3 is pretty bad
0.1 is terrible
What does this CRFI NOTAM tell us and how would we use it to find out how much longer our landing roll will be?
CYWG CRFI 18/36 -10 .30 0401191055Z
WYG CRFI for RWY 18/36
Temp -10oC
CRFI is 0.3
Taken at 2004, Jan 19, 1055Z
AC normally takes 1800ft to stop
With a CRFI of 0.3, it will now take 3970ft
How are the CRFI and Crosswind components used together?
Crosswind charts in the CFS provide the minimum CRFI for a given crosswind.
Calculate the headwind and crosswind as normal and then extend a verticle line down from the crosswind value to find the recommended minimum safe CRFI value for this crosswind.
If after calculating the min CFRI we see a NOTAM that indicates a RWY has a CRFI value that is less than what the crosswind chart suggested we should be wary
The greater the crosswind component, the _________ CRFI will also need to be so that you are able to maintain directional control on the landing roll
The greater the crosswind, the greater the CRFI value must be
CRFI Sample Problem
What is the first thing you should be doing when there is any question that involves a performance chart?
Calculating the pressure altitude
What is the Accelerate-Stop speed?
The distance it would take for your AC to start on the take off roll and get to V1, then pull the power and come to a complete stop
What is the Accelerate-Go Distance?
The total distance required to accelerate the AC to a specified speed and, assuming failure of an engine at the moment that speed is attained, continue takeoff on the remaining engine to a height of 50ft.
How do you use a x-wind chart?
- Find the value of the wind speed on the headwind side
- Follow the curve down to however many degrees off the runway the wind direction is
- Where they intersect, go straight down for the x-wind componenet and straight to the left for the headwind component.
- Keep going straight down for the max CRFI allowed if there is one
If the exam gives you a x-wind chart and asks something like “With a stalling speed of 50KTS, what is the maximum wind component?” how do you use the x-wind chart?
You times the stall speed they gave you by 0.2. In this case 50 x 0.2 = 10.
You take this value and go up from the bottom of the graph (the x-wind component) and draw a line up to the degrees off runway line. Then follow the curve back down to the x-wind line on the bottom of the graph. This is the max allowable x-wind for when the wind is that many degrees off the runway.
