Climb Gradient Question

[heywatchthis]

I know, I know everyone is sick of this. And yes I did do a search and found tons of info previously discussed.

Background?

An obstacle-free departure flight path is based on your aircraft climbing at least 200 feet per nautical mile, after it crosses the end of the runway at least 35 feet above the ground. In addition, you must be able to climb to 400 feet above the airport elevation within 2 nautical miles, before reaching a point where a turn is required. (IE 200 FPNM)

ALSO?

A slope of 152 feet per nautical mile is assessed for obstacles. If no obstacle penetrates this slope, the 200 feet per nautical mile climb gradient provides you with a minimum of 48 feet of obstacle clearance for each mile of flight. If obstacles do penetrate this slope, special avoidance procedures such as ceiling and visibility minimums, detailed flight maneuvers, and/or greater climb gradients are specified.

QUESTION?

If there is an obstacle just under the 152 fpnm (say 150 fpnm), then you will have no indication of an obstacle and it is considered an obstacle free departure flight path.
BUT in order to make the standard 200 fpnm requirement to 400 ft, you would need a climb gradient of 3.29%. (200 / 6076 *100)

If you take off at a weight that gives you the minimum climb gradient for 2nd segment climb of 2.4% gross, and a 1.6% net, seeing how you know of no obstacles...
YOU WILL NOT BE ANYWHERE NEAR 3.3% AND COULD HIT THE OBSTACLE.

So why the heck do we need to make a minimum 2.4 % climb, when obstacles are assessed up to 3.3% climb gradient with no warning?

 

[guido411]

This is why a 3.3% gradient is required to depart IFR (below 1000-3) in a Part 25 airplane. The 1.6% gradient is for VFR departures which should allow you the ablity to see and avoid the obstacle.

 

[heywatchthis]

This is why a 3.3% gradient is required to depart IFR (below 1000-3) in a Part 25 airplane. The 1.6% gradient is for VFR departures which should allow you the ablity to see and avoid the obstacle.

OK, good answer! Where does part 25 state VFR Versus IFR departures?

 

[Doc Holiday]

It doesn't. Part 25 only specifies what is required for certification of aircraft. Minimum climb gradients are included in this, but they are not related in any way to instrument procedures.

121.189(d) or 135.379(d) tells you what minimum obstacle clearance needs to be for the net takeoff flight path (35 ft above and 200 feet horizontally, etc. etc)

121.651 and 91.175 say that operators for hire cannot takeoff with weather less than that prescribed in Part 97 (your DPs and ODPs). If no climb gradients are published in a DP or ODP, then 200 ft/nm (3.3%) is required. AIM 5-2-7

The 1.6% net (2.4% gross) mentioned above is the absolute minimum 2nd segment climb gradient allowed. Taking off at a weight higher than would allow that gradient in case of an engine failure (2 engine airplane) would be exceeding an AFM limitaion.

 

[Wantfrys]

but were does it actual say "in case of engine failure"

 

[ttflyer]

The point of all these numbers is that you have to assume you are going to lose it, and still be able to meet the minimum performance requirements to clear obstacales.

 

[LJ45]

Lead sled....Help us! LOL

 

[gunfyter]

but were does it actual say "in case of engine failure"

It says it in part 135. Under 91 there is no requirement to make the TERPS climb gradient in the event of an engine failure....

 

[ttflyer]

It says it in part 135. Under 91 there is no requirement to make the TERPS climb gradient in the event of an engine failure....

Agreed. But the FAA can still violate you (part 91) under the careless and reckless catch all. Like most of 91, you would probably have to crash to get their attention...

If I can't meet the TERPS IFR, I depart VFR (if I can safely do so). If I can't depart VFR, I don't go...

 

[Wantfrys]

It says it in part 135. Under 91 there is no requirement to make the TERPS climb gradient in the event of an engine failure....

Ok first were in 135 I have got into heated talks with guys at Flight Safety about this. Also I know there is a difference with Part 25 ,27 but are you telling me that a PC-12(Single engine) would never be able to departe under IFR under P-135?

 

[MauleSkinner]

but were does it actual say "in case of engine failure"

Even Part 91 requires large and turbine-powered multiengine airplanes to use AFM data for takeoffs. I have yet to see an AFM for a large, turbine-powered multiengine airplane (I haven't flown any piston ones that qualify, so I can't say there) that gives all-engine takeoff data, which means you have to calculate it for the engine failure.

but are you telling me that a PC-12(Single engine) would never be able to departe under IFR under P-135?

The PC-12, I"m sure, has all-engine takeoff data in its AFM. (in this case, all-engine is only one engine.) However, since I believe it's a Part 23 (small--12,500# max) airplane, its AFM would be more similar to a King Air's, which also has two-engine data, which would then be allowed for most of these computations.

Fly safe!

David

 

[Wantfrys]

First, thank you for your reply,but I still have questions. A be-400 is under part 25 the afm does have two engine climb chart. The other arguement is under 135.379 it talks about large transport category, but nothing about one engine inop. So in a case of a F-900 do you use one engine out, two or all engine operating. The guys in Flight Safety use the argument from 135.379 to say that you take all engines operating.

 

[guido411]

Ok first were in 135 I have got into heated talks with guys at Flight Safety about this. Also I know there is a difference with Part 25 ,27 but are you telling me that a PC-12(Single engine) would never be able to departe under IFR under P-135?

First of all I think it's Part 23 (small aircraft certification) not Part 27 that you're referring to. And lets get serious, are you really asking if you have to consider climb out if you have an engine failure in a PC-12? Part 23 airplanes are exempt from garunteed OEI climb rules. Part 25 airplanes, whether operating under 91, 135, or 121 must garutnee a 1.6% gross OEI climb IFR or VFR. Under commercial operations you must be able to meet the TERPS requirement of 3.3% (unless the chart dictates more) if you are operating in IFR conditions.

As for a be400, it is considered a "large" airplane bacause its MGTOW is greater than 12,500#. As is a F-900. You're correct, there IS a chart showing both engines operating climb but you HAVE to assume you'll lose one of those engines (OEI) during takeoff at the most critical time. The 2 engine climb chart in a be400's AFM is really just a nice to know chart but not relavent. A F-900 is subject to the same rules, they must consider ONE of the engines (the most critical so not the center) failing at V1. So in answer to your question, a F-900 has to be able to meet 1.6 (3.3 or more under IFR) with TWO engines operative.

 

[gunfyter]

I believe the two engine climb chart is FAA Accepted... not FAA APPROVED

 

[ultrarunner]

So in a case of a F-900 do you use one engine out, two or all engine operating.

The rules change with three-holers, but the game remains the same. If you're departing IFR and you become One-Engine-Inoperative, meet the gradient or meet your maker!

The gradients are slightly different with three-holers, since you're loosing only 1/3 your thrust as opposed to 1/2 your available thrust with a twin.

 

[murfdawg998]

Thanks everyone for the discussions...for me this has been all very timely, relevant stuff. I'm going to EGE tomorrow.

MURF

 

[Beechjetr]

\ A be-400 is under part 25 the afm does have two engine climb chart.

What AFM do you have? SHOW me the 2 eng climb chart for a be-400.

 

[MauleSkinner]

What AFM do you have? SHOW me the 2 eng climb chart for a be-400.

Landing climb

 

[Beechjetr]

Landing climb

couple issues...

Associted Conditions
Flaps - 30
Gear - Down

 

[Lead Sled]

It says it in part 135. Under 91 there is no requirement to make the TERPS climb gradient in the event of an engine failure...

True

If I can't meet the TERPS IFR, I depart VFR (if I can safely do so). If I can't depart VFR, I don't go...

Smart

...I have got into heated talks with guys at Flight Safety about this...

Me too; however, that was then, this is now. In the past, comparative few instructors at the various training centers understood the concepts. Fortunately, the tide is turning and nowadays you are more likely be able to get the straight scoop in performance class.

Do not confuse aircraft takeoff performance certification requirements with TERPS obstacle clearance requirements. They are apples and oranges.

The aircraft performance charts essentially only get you to 1,500' AGL with the loss of one engine. PERIOD. In other words, if you lose an engine on takeoff, the charts will guarantee that you can climb up to pattern altitude from which point you can come back around to the airport and land - nothing more.

The climb profiles on the departure procedures tell you what you have to be able to do to keep your nose out of the dirt. These requirements can (and usually do) extend well beyond 1,500' AGL - well off the takeoff performance charts.

We don't have all engine operating climb charts for our airplanes. The manufacturers aren't required to provide them and normally don't. (I haven't seen a Beechjet AFM.)

Under part 91, there is no requirement to be able to achieve the climb profiles on the departure procedure with an engine out. Under part 121 or 135 you do OR have an alternate procedure. Taking Aspen as the ubberexample, you either have to be able to have enough ceiling and visibility to see and avoid the terrain, or have the engine-out climb capability to out climb it. (Remember though, your takeoff performance charts only get to you 1500' AGL, not 14,000' MSL - in spite of what your perfromance class instructors have told you, you cant extrapolate them beyond 1500' AGL.) or have an alternate departure procedure available to you to use in the event of an emergency - the loss of an engine. The 121 guys at Aspen all use the alternate departure procedure. Ditto for many 91 and 135 operators.

I've said it previously, if I wanted to wreak havoc among the flight crew operating out of the "ski country" airports, I wouldn't ramp check them prior to departure - I'd do it immediately after landing and have them show me their approach climb charts.

LS