FlightAware Discussions

:?: KEGE Gypsum SID climb gradient- TERPS Geeks only plz


Okay, this is for all the performance geeks in the crowd.

Departing KEGE on the Gypsum SID, in IFR or MVFR conditions (i.e. <4100-3) is the required gradient figured one engine inop or not? (I have seen both opinions.) I have heard the opinion that using all-engine climb numbers is acceptable. I am dubious, though.

If one engine inop, do I use NET or GROSS? My understanding is that the SID specifies GROSS, and if I use NET from the book, I am doubling the safety margins (35’ dry RW, + .8% + 24%of overall gross gradient). If so, I should be able to subtract .8% from required (or add it to my AFM/FMS numbers) to compensate, yes?

I also think I can factor in the unused runway portion, as the SID assumes that I am crossing the departure end at 35’, and even engine-out I will beat that by quite a bit. I know how to do this for a height/distance obstacle problem, but how do I add credit for it in a required SID gradient?

NOTE- This seems to be a post TERPS Change-19 SID. So, the safety margin went from the old 48’/NM to 24% of the overall gradient.

If I cannot make the climb, and I wait for 4100-3, do I climb in VMC circling over the field and head NE and pick up the 212 radial to RLG? (That’s what the chart says.) I am afraid that if I did that, the tower controllers would freak out and wonder what the hell I am doing.
It seems that everyone just blasts off IMC or not and flies the procedure as charted.

I see aircraft from Beechjets to CE750s blasting out in IMC and flying the RW25 departure route. The way I read it is that if you can’t make the gradient, you can’t fly the KIRLE part of the SID. Period. Am I missing something?


What are you flying?

Can you depart with enough fuel to make it to KAPA then get fuel to make it to your destination?

It’s been two years since I flew out of that airport but I remember that departure and we did it in a LJ25 and had to take off with hardly any fuel and land at KAPA (I Think that’s were we fueled up)


We go in in both the G150 and GIV.

The GIV is a strong performer, but can’t make 13% one engine inop. The G150 does alright, but isn’t great. But it does have the option of a Flaps 0 takeoff, which places in pretty close to enroute climb configuration with only slat retraction to deal with on third segment.

Change 19 to TERPS took place in DEC of last year, so the GROSS gradient required per the SID is now higher (now 24% of overall instead of 48’/NM). So that may be why you remember being able to do it.

I am really wondering how guys are making the numbers work for the Gypsum Departure. I saw a DAL 757 do it, and I know those guys are running good numbers (runway analysis charts/program), but the corporate numbers just don’t seem to workout.

Are guys just blindly blasting off and flying the RW25 departure as charted without consideration?

The only answer I see is to fly the RW7 departure, which I can make gradient on pretty easily. But, ATC isn’t fond of it and they make us wait 20-30 mins sometimes before letting us go.

I am wondering if there is something I am missing, like factoring in unused runway, eliminating “double margins” in GROSS v.NET, or carrying a cargo compartment full of helium balloons.


It sounds like you are asking about part 25 or maybe part 23 commuter aircraft .
For part 91 runway required and second segment are the only takeoff calculations that you have to do that assume an engine out. Visual climbs, SID/DP climb gradients as well as minimum weather specified in the departure procedure are all mandatory even for part 91 but can be calculated using everything you have. Even if you never see anyone else climb over the airport you can verify with the tower before takeoff that you will be doing it, they know the procedure exists.

Make sure your airplane will turn in the valley. We did an exercise two or three years ago at Flight Safety, the airplane I fly (G2) will not make a turn on one engine within the valley at Eagle and still climb unless you have just enough fuel to only go around the pattern once. We all remember our private pilot instructor teaching 60 degree bank turns and the effect on stall speed. What I never learned until just a few years ago is your lift is cut in half at 15 degrees of bank. That is why a maximum of 15 degrees of bank is built into low altitude turns on departure procedures. Most mountain airports require much more bank than that to turn and stay within the valley.

I flew for one 91 operator that had a policy that said we always calculated a 2 engine climb to the end of the DP or obstacle clearance even if it was just an exercise. In addition, if the weather was clear, we could calculate, and use, just the runway and second segment climb as required since if you lost one you probably were returning for a VFR landing anyway. If the clouds rolled in but the airport was above approach minimums we also calculated a OEI climb to the appropriate approach segment. If it was below minimums we calculated to the end of the DP on one. In that case we also had to calculate climb gradients towards a takeoff alternate since that airport might be in a different direction. Sometimes having a plan B let us go out a bit heavier even if it meant going the wrong way for a few minutes. Of course some airports only have one departure so you are stuck.

As long as you have plan B (some call it a bail out procedure) figured out before takeoff you should be in good shape. Losing an engine, the last time I checked, qualified as an emergency so you can switch to plan B with a quick call to ATC, press on, and let them worry about clearing traffic in the meantime. Looking at a sectional chart before takeoff to see if there is a feasible way to go down river to an airport is a perfectly legal way to get out of Dodge, as long as the weather co-operates. :slight_smile:

The airlines have the benefit of huge computer programs that utilize the whole runway. For the most part the rest of us poor slobs have no way to unbalance the field length which generally improves the climb performance just a bit.


Yeah, both G150 and GIV are part 25.

Sounds like you’re in the “all engine climb for SID gradient” camp.

But, my understanding is that we must use one engine inop climb data for any SID/DP unless the notation in the Jepp says “ATC” on the required gradient. This would indicate that ATC could then “scatter” the other traffic for which we were climbing so aggressively to avoid. Kinda hard to scatter the granite. Without a published or approved Special Engine Out Procedure, you are basically flying without any guidance re minimum altitudes for obstacle avoidance.

Most DPs address this through the use of weather minima, the idea being see and avoid the terrain. But the Gypsum departure has separate path to be flown if using the 4100-3 weather minima. (see chart)

The GIV AFM has a special section addressing this, but is specifies that it is for use on ATC-required climb SIDs only (i.e. SFO to avoid the OAK DEP/ARR corridor). The SID/DPs were even recently relabeled to indicate when gradients were required for ATC or terrain clearance purposes.

If there is a reading on the FARs that allows the use of all-engine climb performance to meet non-ATC climb gradients I’d love to see it. If there is an opinion issued on the subject from an authoritative source please post a link.


We did quite a bit of research on the subject but that’s been about 15 years ago so I don’t remember offhand where the legalities were published. Probably the AIM or deeeeep in the TERPS. I agree that not using some discretion may not be the best but, unless the rules have changed, it is legal to use 2 engine data. 135 is another ballgame, maybe you heard it from a charter operator.
I work overseas now so I don’t always hear about some of the changes like the recent change you mentioned.

lol, I know the G4 and G150 are part 25, I didn’t notice that you were also the original poster.


Here are a couple of pages I just found. I haven’t read them entirely yet but they look like a good place to start.


airweb.faa.gov/regulatory_an … 120-91.pdf

The second one is for non 91 operators but it references TERPS, FARs and PANS-OPS which are for everybody.


In IMC or less than 4100-3 conditions you need to plan it on one engine. FAR-25 requires that you can meet all then performance.

If you can’t climb 815’/nm one engine, accept the clearance, depart and lose one at V1 or shortly there after your f*cK#d. You’ve placed yourself in a position, IMC and climbing slower than the terrain, that can’t be won.

That is why they have the Visual option, (4100-3) this lets you get up to 10500 in VMC so you can provide your own visual terrain clearance if you lose on and come back for landing or continue on to Kremmling on the 212 radial in IMC because the gradient from 10500 to 1200 is Kansas like.

If you don’t like those you could determine your own ceiling required to circle in the valley, (more like a canyon) to come back. Plan a two engine climb to that go-no-go point. plot a single engine climb from there to 12,000 and see if that stays above the gradient.
I know one operator that does this with some custom software. I personally don’t like it because I don’t like planning oh shit bailout maneuvers. I’d prefer to say “damn, #1’s rolling back” keep going & “tell center we need to go to Grand Junction, then get me a coffee”


That’s what I thought. It is my understanding that as we fly Part25 aircraft, we MUST consider all planning from V1 to the enroute portion (or a doable alternative) with one engine out.

But, I see folks launching in aircraft that I KNOW barely make gradient on all engines. It’s a good thing turbine engines are so reliable. I am just waiting for the day when we wake up and see where someone put a Beechjet or Citation into the side of that mountain.

But, if one takes into account unused runway (pretty significant on some aircraft), and figures total gross climb to 12000MSL/2539’AGL which includes the last 1000’ in the enroute climb configuration there may be a way to meet it. The enroute climb (that is the post-1500AGL, clean wing, engines at MCT portion) is usually a much better than second, third, and final segment.

It is my understanding, also, that holding V2 to 2539’AGL isn’t acceptable per FAA. V2 only exists as high as the manufacturer’s charts (either 400AGL, 1000AGL, or 1500AGL). Also, not a good idea because enroute climb data is almost always better than second segment, despite having a much lower Part25 requirement.


Are we talking what is legal, or what we should be doing as professionals?

According to one of the articles I posted equipment failures are not part of TERPS. A 172 has the same requirements as a civilian B-52. Part 25 only says what the airplane must be able to do under certain conditions and what data to provide to the pilots. Arguably we don’t get all the data we need, but more than we want at checkride time!

I agree that we should, as professionals, be planning for the worst case, but part 25 only gives us the data telling us whether or not we will be able to climb to 9,000 or 12,000 ft. The procedure specifies at what gradient but does not require us to figure it with one engine out. The decision to plan it with OEI is left up to our professionalism.
The visual climb to cross the airport at or above 10,500 on the way towards Kremmling only reduces the required climb gradient to standard. We also still have to be sure the airplane we are flying that day can maneuver in the valley.


I’m talking about what we should be doing/planning as professionals.
I’ve never payed much attention or gave a damn to legal beyond CYA on paper or checkrides.

I had a checkride or two where the examiner got miffed because I refused to accept a clearance or perform maneuver. In each debrief I was shown and beaten up over the maneuver or clearance being legal. My response was always that it wasn’t the safest option and I chose what I do with my aircraft not ATC or the FAA.

There are a lot of legal things that are dangerous and a few safe things that might not be legal.

I comply with safe then legal. The problem occurs when Rockstar/Cowboy charter blasts off with 8 pax and goes non-stop and your sitting w/ 4 pax and have to delay till the temps or weather is better and still require a stop in the same aircraft type. :imp:

You don’t need another pilot/A&P for that G-IV, Do ya??


Sounds a lot like like my mantra- Not all that is safe is Legal and not all that is legal is safe


Well said, I’ve postponed a few flights out of Aspen while other guys were disappearing into the snow shower. Even got ripped by the Chief Pilot for spending an extra night, but he was one of those former cowboy/charter pilots who didn’t think twice about over gross takeoffs or landings or scud running around the LA basin in a jet.


and we must plan the missed approach on one engine as well. It would be a bad day to not see the runway at the bottom of an approach and fly into cumulus granite on the missed. If I remember right Burbank and Sun Valley both have steep missed approach gradient requirements.


Leaving EGE a couple months ago, the weather was down, but just enough to see the mountainside, but not the tops. We were NOT going to leave, along with about 75% of the other guys. The clients saw a Hawker 800 taxi out and said “How come he can leave?” I said let’s watch him takeoff (knowing that every H25B looks awful coming out of that place,) he used about 80% of the runway, and his climb was so shallow as he made the left turn, it appeared as if he barely cleared the mountains before disappearing. I turned back to the client, and said, “Because WE don’t do THAT!” He understood completely, and didn’t complain again.


Although i must Disagree that single engine loss ROC for a 172 is vastly different than a B52 (Snicker)


lol but the terps make no distinction.


Departure procedures are all engine procedures and have nothing to do with single engine performance. (except as stated below)

Climb performance is specified in the regulations. For 135 operations you must meet the requirements of 135.397. Basically you need to clear all obstacles with a net takeoff flight path of 35 feet vertically (135, large transport). Horizontal is now 1500 feet, if I remember correct, per an AC that the FAA put out.

To determine if you can meet the climb requirements you can use a couple of different methods. The easiest and best method for increased takeoff weight is runway analysis. Companies like Aircraft Performance Group (APG) base their analysis off of the departure procedure or make a special procedure to help increase weights. Departure procedures provide greater clearance vertically and horizontally from terrain than runway analysis which is why analysis usually provides a lot better numbers.

If an operator does not subscribe to runway analysis they need to have another way of determining required obstacle clearance. This is why you find a lot of people using the departure procedure (single engine) as their source of climb numbers.

One thing that many people make a mistake on is that this is a climb regulation regardless of weather. If you are a 135 operation and use the departure procedure to prove climb requirements, it must be done in all weather conditions, IFR to clear and a million. The same applies to runway analysis.

There is not a planning option of taking off and flying down the valley or circling back to the airport in VFR conditions when flying 135. You must be able to back up those options with the proper data.

For more info than you ever want to know on this, check out the videos on the right side of this website. apg.aero/MW/

I have done a lot of research on this, but it has been a few years.

Hope this helps.


AC 120-91. Terps are two engine, normal procedures. Engine loss is an emergency. You are NEVER required to show that you can do the SID single engine. And AC 120-91 says that even if you do show you can meet the specified climb requirement one engine, you are still not guaranteed obstacle clearance, because a SID is flow differently than an engine out procedure. READ AC 120-91.