Multi Engine Aircraft Certification - Engine Loss Performance

[Thilo]

Hi

I am looking for the FAA certification regulations (Part 21 ?) pertaining the performance of an aircraft after an engine failure.

If I recall correctly, an aircraft that has a MAUW below 12'500 lbs (5'700 kg) does not have to demonstrate during certification the ability to maintain altitude or climb.

Can someone point me to the regulation covering this.

Much appreciated,

Thilo

[Genghis the Engineer]

If nobody beats me to it, I'll post an answer later when I have my library to hand.

However, the answer will be in part 23, and I dont *think* you are correct - I am pretty sure that all twins have to demonstrate a rate of climb single engine.

G

[Genghis the Engineer]

Here you go, CS.23 issue 4 (FAR-23 should be pretty similar)...

CS 23.67 Climb: one-engine-inoperative
(a) For normal, utility and aerobatic category
reciprocating engine-powered aeroplanes of
2 722kg (6 000 lb) or less maximum weight the
following apply:
(1) Each aeroplane with a VSO of more than
113 km/h (61 knots) must be able to maintain a
steady climb gradient of at least 1·5% at a
pressure altitude of 1524 m (5 000 ft) with –
(i) The critical engine -inoperative
and its propeller in the
minimum drag position;
(ii) The remaining engine at not
more than maximum continuous power;
(iii) The landing gear retracted;
(iv) The wing flaps retracted; and
(v) A climb speed not less than
1·2 VS1.
(2) For each aeroplane with a VSO of
113 km/h (61 knots) or less, the steady gradient
of climb or descent at a pressure altitude of
1524 m (5 000 ft) must be determined with –
(i) The critical engine inoperative
and its propeller in the
minimum drag position;
(ii) The remaining engine at not
more than maximum continuous power;
(iii) The landing gear retracted;
(iv) The wing flaps retracted; and
(v) A climb speed not less than
1·2 VS1.
(b) For normal, utility and aerobatic category
reciprocating engine-powered aeroplanes of more
than 2 722 kg (6 000 lb) maximum weight and
turbine engine-powered aeroplanes in the normal,
utility and aerobatic category –
(1) The steady gradient of climb at an
altitude of 122 m (400 ft) above the take-off
surface must be measurably positive with –
(i) The critical engine inoperative
and its propeller in the
minimum drag position;
(ii) The remaining engine at takeoff
power;
(iii) The landing gear retracted;
(iv) The wing flaps in the take-off
position(s); and
(v) A climb speed equal to that
achieved at 15 m (50 ft) in the
demonstration of CS 23.53.
(2) The steady gradient of climb must not be
less than 0·75% at an altitude of 457 m (1 500 ft)
above the take-off or landing surface, as
appropriate with –
inoperative
and its propeller in the
minimum drag position;
(ii) The remaining engine at not
more than maximum continuous power;
(iii) The landing gear retracted;
(iv) The wing flaps retracted; and
(v) A climb speed not less than
1·2 VS1.
(c) For commuter category aeroplanes, the
following apply:
(1) Take-off: landing gear extended.
The steady gradient of climb at the altitude of
the take-off surface must be measurably
positive with –
(i) The critical engine inoperative
and its propeller in the position it rapidly
and automatically assumes;
(ii) The remaining engine at takeoff
power;
(iii) The landing gear extended, all
landing gear doors open;
(iv) The wing flaps in the take-off
position(s);
(v) The wings level; and
(vi) A climb speed equal to V2.
(2) Take-off: landing gear retracted.
The steady gradient of climb at an altitude of
122 m (400 ft) above the take-off surface must
be not less than 2·0% with –
(i) The critical engine inoperative
and its propeller in the position it rapidly
and automatically assumes;
(ii) The remaining engine at takeoff
power;
(iii) The landing gear retracted;
(iv) The wing flaps in the take-off
position(s); and
(v) A climb speed equal to V2.
(3) En-route. The steady gradient of
climb at an altitude of 457 m (1 500 ft) above
the take-off or landing surface, as appropriate,
must be not less than 1·2% with –
(i) The critical engine inoperative
and its propeller in the minimum drag
position;
(ii) The remaining engine at not
more than maximum continuous power;
(iii) The landing gear retracted;
(iv) The wing flaps retracted; and
(v) A climb speed not less than
1·2 VSI.
(4) Discontinued approach. The steady
gradient of climb at an altitude of 122 m
(400 ft) above the landing surface must be not
less than 2·1% with –
(i) The critical engine inoperative
and its propeller in the minimum drag
position;
(ii) The remaining engine at takeoff
power;
(iii) The landing gear retracted;
(iv) The wing flaps in the approach
position(s) in which VSI for these
positions(s) does not exceed 110% of the
VSI for the related all-engines-operating
landing position(s); and
(v) A climb speed established in
connection with normal landing
procedures but not exceeding 1·5 VSI.

Lots of detail, but the executive summary is "yes, there's a minimum climb rate SE".

G

[john_tullamarine]

.. but read carefully for twins less than 6000lb and stall less than 70 mph (61 kt if you prefer merertrification ...)

[Thilo]

Thanks Genghis. Very much appreciated.
Thilo

[JOE-FBS]

Not forgetting that CS / FAR 23 have recently moved to a less prescriptive format with the aim of allowing innovation. CS-23 amendment 5. I don't know the FAR 23 amendment number but just copied from the FAA website the new FAA wording is:

§23.2115 Takeoff performance.
(a) The applicant must determine airplane takeoff performance accounting for—

(1) Stall speed safety margins;

(2) Minimum control speeds; and

(3) Climb gradients.

(b) For single engine airplanes and levels 1, 2, and 3 low-speed multiengine airplanes, takeoff performance includes the determination of ground roll and initial climb distance to 50 feet (15 meters) above the takeoff surface.

(c) For levels 1, 2, and 3 high-speed multiengine airplanes, and level 4 multiengine airplanes, takeoff performance includes a determination the following distances after a sudden critical loss of thrust—

(1) An aborted takeoff at critical speed;

(2) Ground roll and initial climb to 35 feet (11 meters) above the takeoff surface; and

(3) Net takeoff flight path.

[Genghis the Engineer]

My take on the new CS/FAR 23 "consensus standard" approach is that for the time being you're stuck with a lot of negotiation with your authority to get anything through as there isn't yet published list of accepted means of compliance with it, and quite probably they won't allow cherry picking on existing aeroplanes. I should stick with the standard on the TCDS, or issue 4, rather than getting caught in a negotiating spiral with your authority.

G

[JOE-FBS]

That sounds like excellent advice.