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.