Far 25.111

[Gwadwerc]

FAR 25.111 (c)(3)(i) requires a two engine, transport category aircraft to maintain at least a 1.2% climb gradient beginning 400' HAA. How does this mesh with a diverse departure procedure, which requires 200'/NM (or a 3.3% climb gradient) (both engines operating) beginning 400' HAA? Thanks for clearing this up!
-Gwadwerc

 

[mar]

I'll take a stab

Apologies for a wishy-washy response, but most of my books are still packed away from a recent move.

But if I recall correctly, the "diverse" departure is a turning maneuver.

And if I'm not mistaken, the requirements to be met under FAR Part 25 are based on a "straight-out" departure path.

Maybe that will account for what seems like a discrepancy.

If we're lucky a performance engineer will chime in.

Hope that helps (a little).

 

[MauleSkinner]

FAR 25.111 (c)(3)(i) requires a two engine, transport category aircraft to maintain at least a 1.2% climb gradient beginning 400' HAA. How does this mesh with a diverse departure procedure, which requires 200'/NM (or a 3.3% climb gradient) (both engines operating) beginning 400' HAA? Thanks for clearing this up!
-Gwadwerc

It doesn't...FAR 25 is aircraft certification, and has nothing to do with obstacle clearance, other than the fact that they require the charts in the AFM with which to compute obstacle clearance.

fly safe!

David

 

[Gwadwerc]

Thanks gents!

 

[GVFlyer]

Deleted...

 

[GVFlyer]

Mauleskinner is correct. What are you guys doing reading FAR Part 25, it's for aircraft manufacturers - Part 121 and Part 135 set forth operational requirements. TERPS establishes procedures and clearances. The AFM contains certified data for your specific aircraft.

GV

 

[mar]

If accurate, the more info, the better

What are you guys doing reading FAR Part 25, it's for aircraft manufacturers - ...

Sure. But it's helpful to learn why things are designed the way they are.

One example: Accelerate/stop data based on the use of just brakes (no thrust reverse).

To me, that's helpful.

 

[GVFlyer]

Sure. But it's helpful to learn why things are designed the way they are.

One example: Accelerate/stop data based on the use of just brakes (no thrust reverse).

To me, that's helpful.

Fair enough.

In the GV/G550 Airplane Flight Manual take-off data, no credit is given for use of thrust reversers on dry runway Reference Accelerate-Stop distance or Reference Accelerate-Go distance charts. Thrust reverser use is factored into values given for wet runway rejects.

Additional flight test take off data is provided for:

Effective runway length required (flaps 10 and 20).

Takeoff speeds and distances flaps 10 and 20, anti-skid and ground spoilers operative or inoperative.

Runway length and V1 adjustments.

Maximum allowable takeoff gross weight permitted by takeoff climb requirements.

Maximum allowable takeoff gross weight limits due to tire speed and landing brake kinetic energy.

Net takeoff flight path.

Final takeoff climb.

Distance to accelerate from V2 to VSE at 1,500 feet AGL.

Enroute climb.


For GV/G550 Airplane Flight Manual landing data, no credit is given for use of thrust reversers but the use of thrust reversers will result in distances less than those computed for the charts and will significantly improve brake wear characteristics.

Additionally, flight test landing data is provided for:

Anti-skid operative or inoperative

Ground spoilers armed and automatically deployed on touchdown or manual speedbrakes after landing.

Ground spoilers inoperative.

Reduced flap or no flap landings.

Contaminated runway operations.

Max allowable landing gross weight for brake kinetic energy limit.

Over weight landing data (BKE, speeds and distances).

Landing distance using twin-engine reverse thrust only.


As you can see, the company tried to give you a lot of specific data to work with in the AFM.


GV

 

[Coool Hand Luke]

Mauleskinner is correct. What are you guys doing reading FAR Part 25, it's for aircraft manufacturers - Part 121 and Part 135 set forth operational requirements. TERPS establishes procedures and clearances. The AFM contains certified data for your specific aircraft.

GV

The "AFM certified data" that you mention above is derived from the FAR part 25 certification process, specific to each make/model. So, to answer his question, he needs both. TERPS's establishes the climb gradient that you will need to make (departing IFR of course, because as we all know, when VFR it's see and avoid, Ops Specs not withstanding) and your AFM data, as derived through the certification process under FAR part 25 will tell you how well you can reasonably expect your aircraft to perform. So, reference your FAR part 25 AFM data and make adjustments accordingly to meet the requirements for your specific TERPS IFR departure (TERPS doesn't care if you are single-engine, no-engine or all engine, by-the-way...that's a part 25 requirement (and a part 135/121 requirement, but not part 91)...all TERPS cares about is that if you are launching into the soup you gotta make the gradient). TERPS analysis is conducted only at airpots served by an instrument procedure. If an airport is surveyed and is found to not have any "non-standard" (40:1 penetrations) obstructions then a "diverse departure" is assigned (by lack of a specific departure instruction, they assume you know that when departing IFR you are a diverse departure operation). So, the diverse departure provides you with a 48' safety margin to depart IFR and make your turn at 400' AGL as long as you promise to climb at 200'/NM.

 

[Coool Hand Luke]

A good reference, and one that is my aviation library:

Solutions for Mean Airports by Richard Aarons, Business & Commercial Aviation, April 2000.

 

[GEXDriver]

The "AFM certified data" that you mention above is derived from the FAR part 25 certification process, specific to each make/model

...your AFM data, as derived through the certification process under FAR part 25 will tell you how well you can reasonably expect your aircraft to perform. So, reference your FAR part 25 AFM data and make adjustments accordingly to meet the requirements for your specific TERPS IFR departure...

I think GVFlyer probably knows that as he is a Gulfstream Aerospace engineering test pilot, but isn't that what he said anyways?

 

[A Squared]

Nobody has really responded to the actual question raised by the original poster, that is that a transport category aircraft with an engine shut down will not necessarily meet the required climb gradient of a diverse departure, or any other departure for that matter, or a missed approach procedure. Any thoughts on that?

 

[mar]

Sort of.

I think his actual question was more along the lines of: What explains the inconsistancy of the requirement under Part 25 for a 1.2% gradient but 3.3% under TERPS.

True, no one really had an answer for that.

My thoughts on your question would be along the lines of....what the hell are you doing flying old crap that won't climb with an engine shut down unless it's DAY VMC???

Fly safe.

 

[Coool Hand Luke]

I think his actual question was more along the lines of: What explains the inconsistancy of the requirement under Part 25 for a 1.2% gradient but 3.3% under TERPS.

True, no one really had an answer for that.

My thoughts on your question would be along the lines of....what the hell are you doing flying old crap that won't climb with an engine shut down unless it's DAY VMC???

Fly safe.

TERPs guys and certificaion guys apparently don't talk to each other, therefore, we have two different sets of criteria applied. As for why they do not agree on one set of rules, I do not know, but that is the reality of it.

 

[A Squared]

My thoughts on your question would be along the lines of....what the hell are you doing flying old crap that won't climb with an engine shut down unless it's DAY VMC???

Aren't you the same guy who once contributed a post in the defense of flying old crap? Something about making you a better pilot or something?

 

[MauleSkinner]

TERPs guys and certificaion guys apparently don't talk to each other, therefore, we have two different sets of criteria applied. As for why they do not agree on one set of rules, I do not know, but that is the reality of it.

In reality, there is no need for the criteria to be the same...TERPS are designed for flight in IMC; whereas certification requirements are the minimum standard for VMC flight, when obstacles can be seen and avoided.

It's really no different than your light twin, which doesn't require ANY climb rate with an engine inop...it's generally ok in VMC conditions, but not taking obstacles into account in IMC can be hazardous to your health.

Fly safe!

David

 

[GVFlyer]

Aren't you the same guy who once contributed a post in the defense of flying old crap? Something about making you a better pilot or something?

It's got to be an educational experience flying an airplane where at night, you set the mixture control on the 4 Pratt & Whitney R-2800's by looking at the 18 foot flame pattern they generate.

GV

 

[Coool Hand Luke]

It's got to be an educational experience flying an airplane where at night, you set the mixture control on the 4 Pratt & Whitney R-2800's by looking at the 18 foot flame pattern they generate.

GV

Now that is funny!

 

[mar]

Did I say that?

Aren't you the same guy who once contributed a post in the defense of flying old crap? Something about making you a better pilot or something?

Yeah that sounds like something I'd say: Pure brilliance. Thanks for reminding me.

It's really no different than your light twin, which doesn't require ANY climb rate with an engine inop...it's generally ok in VMC conditions, but not taking obstacles into account in IMC can be hazardous to your health.

Actually, there is (was) a requirement for a positive rate of climb on light twins

Ref: http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/67a6f26638f5b1c385256687006b9239!OpenDocument&ExpandSection=-3

The link above is the old FAR airplanes used to be certificated under. The next link is the new FAR pertaining to, obviously, new airplanes: http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/2459CA427595FBF685256687006BC958?OpenDocument

 

[MauleSkinner]

Actually, there is (was) a requirement for a positive rate of climb on light twins

Ref: http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/67a6f26638f5b1c385256687006b9239!OpenDocument&ExpandSection=-3

The link above is the old FAR airplanes used to be certificated under. The next link is the new FAR pertaining to, obviously, new airplanes: http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/0/2459CA427595FBF685256687006BC958?OpenDocument

You are correct. I should have said, "...which may not require ANY climb rate with an engine inop...", as aircraft under 6000 lbs with Vso less than 70 mph/61kts (depending on the reg) show up with no positive climb requirements.

I'm sure that aircraft certificated under CAR 3 or Aeronautical Bulletin 7A have less stringent requirements yet, so it's also important to know the basis under which your airplane was certificated.

Fly safe!

David