12,600 FT
STANDARD DAY
(Point A)
900 1,000 1,100 1,200 1,300 1,400
GROSS WEIGHT - LBS.
425 450 475 500 525 550 575
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
PRESSURE ALTITUDE - Hp X 1,000 FT.
OAT
°C °F
– 20 – 4
+ 14
+ 32
+ 50
+ 68
+ 86
+ 104
– 10
+ 10
+ 20
+ 30
+ 40
0
OUT OF GROUND EFFECT
FULL THROTTLE ( OR LIMIT MANIFOLD
PRESSURE) AND 104% RPM
GROSS WEIGHT - KGS.
MAX CONT. OR FULL THROTTLE
OGE HOVER CEILING VS. GROSS WEIGHT
600 625
–20
–10
+10
+20
+30
+40
0
OAT °C
(Point B)
(Point C)
Figure 8-3. Out of Ground Effect Hover Ceiling versus Gross
Weight Chart.
As density altitude increases, more power is required to
hover. At some point, the power required is equal to the
power available. This establishes the hovering ceiling
under the existing conditions. Any adjustment to the
gross weight by varying fuel, payload, or both, affects
the hovering ceiling. The heavier the gross weight, the
lower the hovering ceiling. As gross weight is
decreased, the hover ceiling increases.
SAMPLE PROBLEM 1
You are to fly a photographer to a remote location to
take pictures of the local wildlife. Using figure 8-2, can
you safely hover in ground effect at your departure
point with the following conditions?
Pressure Altitude..................................8,000 feet
Temperature...............................................+15°C
Takeoff Gross Weight.....................1,250 pounds
R.P.M..........................................................104%
First enter the chart at 8,000 feet pressure altitude
(point A), then move right until reaching a point midway
between the +10°C and +20°C lines (point B).
From that point, proceed down to find the maximum
gross weight where a 2 foot hover can be achieved. In
this case, it is approximately 1,280 pounds (point C).
DENSITY ALTITUDE
12,600 FT
STANDARD DAY
1,370
(Point A)
(Point B)
900 1,000 1,100 1,200 1,300 1,400
GROSS WEIGHT - LBS.
425 450 475 500 525 550 575
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
OAT °C
PRESSURE ALTITUDE - Hp X 1,000 FT.
OAT
°C °F
– 20 – 4
+ 14
+ 32
+ 50
+ 68
+ 86
+ 104
– 10
+ 10
+ 20
+ 30
+ 40
0
IN GROUND EFFECT AT 2 FOOT SKID CLEARANCE
FULL THROTTLE AND 104% RPM
GROSS WEIGHT - KGS.
–20
–10
+10
+20
+30
+40
0
IGE HOVER CEILING VS. GROSS WEIGHT
(Point C)
Figure 8-2. In Ground Effect Hover Ceiling versus Gross
Weight Chart.
8-5
the entire flight operation. Being able to hover at the takeoff
location with a certain gross weight does not ensure the
same performance at the landing point. If the destination
point is at a higher density altitude because of higher elevation,
temperature, and/or relative humidity, more power
is required to hover. You should be able to predict whether
hovering power will be available at the destination by
knowing the temperature and wind conditions, using the
performance charts in the helicopter flight manual, and
making certain power checks during hover and in flight
prior to commencing the approach and landing.
TAKEOFF PERFORMANCE
If takeoff charts are included in the rotorcraft flight manual,
they usually indicate the distance it takes to clear a 50-
foot obstacle based on various conditions of weight,
pressure altitude, and temperature. In addition, the values
computed in the takeoff charts usually assume that the
flight profile is per the applicable height-velocity diagram.
SAMPLE PROBLEM 3
In this example, determine the distance to clear a 50-
foot obstacle with the following conditions:
Pressure Altitude..................................5,000 feet
Takeoff Gross Weight.....................2,850 pounds
Temperature .................................................95°F
Using figure 8-4, locate 2,850 pounds in the first column.
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