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From 23.2005
Certification levels
Performance Levels
§23.2120 Climb Requirements
a) with all engines operating and in the initial climb configuration
1) For levels 1 and 2 low-speed airplanes, a climb gradient of 8.3 percent for landplanes and 6.7 percent for seaplanes and amphibians and,
2) For levels 1 and 2 high speed airplanes, all level 3 airplanes, and level 4 single-engines a climb gradient after takeoff of 4 percent
(a) For normal, utility and acrobatic category reciprocating engine-powereed airplanes of 6,000 pounds or less maximum weight, the following apply:
(1) Except for those airplanes that meet the requirements prescribed in §23.562(d), each airplane with a Vso of more than 61 knots must be able to maintain a steady climb gradient of at least 1.5 percent at a pressure altitude of 5,000 feet with the -
(i) Critical engine inoperative and its propeller in the minimum drag position;
(ii) Remaining engine(s) at not more than maximum continuous power;
(iii) Landing gear retracted;
(iv) Wing flaps retracted; and
(v) Climb speed not less than 1.2 Vs1
(2) For each airplane that meets the requirements prescribed in §23.562(d), or that has a Vso of 61 knots or less, the steady gradient of climb or descent at a pressure altitude of 5,000 feet must be determined with the -
(i) Critical engine inoperative and its propeller in the minimum drag position;
(ii) Remaining engine(s) at not more than maximum continuous power;
(iii) Landing gear retracted;
(iv) Wing flaps retracted; and
(v) Climb speed not less than 1.2 Vs1
6000 lbs or less
61 knots or less
Part 23 Performance Requirements - 8/30/17 and beyond
After a critical loss of thrust on multiengine airplanes-
Calculating our performance loss on a single engine is vitally important to multi-engine operating. There are several different ways to do so.
ROC x Weight = EHP
33,000
1650 fpm 2 engines 185 fpm 1 engine TO wt. 3730
1650 fpm x 3730 / 3000 = 186.5 185 fpm x 3730 / 33,000 = 20.91
20.91 / 186.5 = 11.2% remaining - 100% - 11.2% = 88.8% performance loss
A more accurate and calculatable way to do single engine performance is using your performance charts for comparing climb rates. For example,
2 Engine ROC = 1650 fpm 1 Engine ROC = 185 fpm
185/1650 = 11.2% remaining or 88.8% loss
Vmc is the calibrated airspeed at which, when the engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative, and thereafter maintain straight flight at the same speed with an angle of bank not more than 5 degrees. The method used to simulate critical engine failure must represent the most critical mode of power plant failure expected in service with respect to controllability.
Critical Engine Inoperative
Operating Engine at Max Takeoff Power
Most unfavorable weight and CG
Most critical mode of powerplant failure represented
Maintain control (no dangerous attitudes, no more than 20 degrees heading change
Inoperative Engine propeller in Takeoff Position
NOT more than 5 degrees bank
in ground effect
more than 150 lb rudder input at max power
Flaps in Takeoff Position
Landing gear retracted
Trimmed for Takeoff
Vmc not more than 1.2 Vs1
There are several different factors that will either raise or lower VMC, making it important for you to understand how each will affect VMC while you're flying with one engine INOP
Rudder effectiveness increases with a foreward CG vs an Aft CG due to the longer arm
Bank angle is introduced to eliminate the sideslipping condition peresent when only rudder is used to maintain a constant heading
Loaded weight has no bearing on the directional controllability of the aircraft until a bank angle is introduced.
Spiraling slipstream is dependant the direction of rotation of the propellers. The effect of an inoperative engine is different based on whether or not we a conventional twin design or counter-rotating propellers.