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kitplane01
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FAA Regs Part 23 vs Part 25

Fri Dec 01, 2017 7:44 pm

Part 23 is the regulation that governs small aircraft. Part 25 is the regulation that governs transport category aircraft. Significant google searching does not tell me what the particular differences are.

Are there lower G limits, more requirements for redundancy, or what? Can someone offer a particular example of a difference between a part 23 and a part 25 aircraft?

-Thanks
 
GalaxyFlyer
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Re: FAA Regs Part 23 vs Part 25

Fri Dec 01, 2017 8:49 pm

You can build a single-engine Part 23; but no such plane under Part 25. A Part 23 twin-engine plane, under 6,000#, essentially must only be controllable, no specified engine-out performance. A normal category Part 23 plane must have structure capable of 3.8G while a Part 25 G design standard is 2.5G.

It’s way more complicated than those examples, but Part 25 is much more rigid and designed for commercial transport, hence a higher standard of care and design.

GF
 
Woodreau
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Re: FAA Regs Part 23 vs Part 25

Sat Dec 02, 2017 3:06 pm

One of the one things that stand out from a pilot's perspective is engine out performance. Both Part 23 and part 25 aircraft are required to publish a performance number in the event of an engine failure.

Under Part 23 the engine out performance after takeoff is not required to be a positive climb (i.e it can be negative into the ground where the remaining engine merely takes you to the crash site.) Under Part 25 the engine out performance is required to be net positive during the first, second, third segment climb. So the aircraft is required to be able to still fly with an engine failure after takeoff.

Just one item as an example as a difference between Part 23 and Part 25 certification.
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
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kitplane01
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Re: FAA Regs Part 23 vs Part 25

Sat Dec 02, 2017 7:34 pm

Woodreau wrote:
One of the one things that stand out from a pilot's perspective is engine out performance. Both Part 23 and part 25 aircraft are required to publish a performance number in the event of an engine failure.

Under Part 23 the engine out performance after takeoff is not required to be a positive climb (i.e it can be negative into the ground where the remaining engine merely takes you to the crash site.) Under Part 25 the engine out performance is required to be net positive during the first, second, third segment climb. So the aircraft is required to be able to still fly with an engine failure after takeoff.

Just one item as an example as a difference between Part 23 and Part 25 certification.


This description seems unfair to part 23. I thought the part 23 rule was that if you cannot climb after engine out, you were certified something like a single engine airplane with a limiting stall speed of 61 kn.

Are there other differences? I think this is an interesting technical question.
 
GalaxyFlyer
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Re: FAA Regs Part 23 vs Part 25

Sat Dec 02, 2017 10:13 pm

There’s scads of differences, try reading the two Parts plus the Acceptable Means of Compliance manuals. It’s a lot of engineering and real experience, but the two rules are completely different. It’s not like Part 25 is a beefed up Part 23. Also, look at CAR 4b, the Part 25 predecessor.

GF
 
N353SK
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Re: FAA Regs Part 23 vs Part 25

Sun Dec 03, 2017 1:43 am

From the FAA:

6,000 pounds or less maximum certificated takeoff weight and Vso 61 knots or less:
The single engine rate of climb or climb gradient at 5,000 MSL must simply be determined. The rate of climb could be a negative number. There is no requirement for a positive single engine rate of climb at 5,000 feet or any other altitude.
Rate of climb is the altitude gain per unit of time, while climb gradient is the actual measure of altitude gained per 100 feet of horizontal travel, expressed as a percentage. An altitude gain of 1.5 feet per 100 feet of horizontal travel is a climb gradient of 1.5 percent.
With regard to climb performance, the light twin with one engine inoperative will perform marginally at best, and may not be capable of climbing at all under existing conditions. There is no requirement that a light twin in the takeoff or landing configuration be able to maintain altitude, even at sea level, with one engine inoperative.


https://www.faasafety.gov/files/events/ ... ements.pdf

Another HUGE difference is the requirement for balanced field length on takeoff of part 25 aircraft:

https://en.wikipedia.org/wiki/Balanced_field_takeoff
 
GalaxyFlyer
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Joined: Fri Jan 01, 2016 4:44 am

Re: FAA Regs Part 23 vs Part 25

Sun Dec 03, 2017 3:03 am

It might be more accurate to say, a Part 25 plane must meet both accelerate-stop and accelerate-go within the runway planed for take-off. Whether those distances are “balanced” (that is, equal) may or may not be true. But, any Part 25 plane will have a V1 speed which enables it to either stop or go. In the stop case, be stopped on the TORA or in the ASDA; or go using the TODA. And climb away, OEI, with the required gradient depending number of engines installed.

Part 23 jets have most of these requirements, but no Part 23 twin engine does, except for commuter category ones.

GF

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