Would be hard to follow an SID with 8% or higher required initial gradient with an engine inoperative.

But then in days gone by we had a pretty conservative performance manual. Standard procedure was to follow the SID and the performance took that into account, only if not possible was there an EOSID on the WAT chart of the runway. Nowadays we would never follow the SID, if no obstacles present (well, obstacles we have to consider) we just fly straight out for the next 30NM by which time we should be above the required minimum altitude.

in days gone by we had a pretty conservative performance manual. Standard procedure was to follow the SID and the performance took that into account

although, presumably, making a profit was not high on the list of priorities ?

we just fly straight out for the next 30NM

in many places that approach imposes a high workload on the ops engineering cell when there may be much simpler general escape techniques available.

Also, the DP may be predicated on noise abatement primarily , resulting in severe weight penalties, when a more economical NTOFP can be constructed that allows greater weight to be carried...As J_T mentions above

:)

FYI: 737 Jock got it right.

Maximum Takeoff Weight Pounds Permitted by Climb
 

I found my own answer with Cessna. This is a certification chart that guarantees you can do at least a 1.2% climb gradient on TWO ENGINES for a Part 25 aircraft.

WTF? 1.2% gradient? You are kidding, correct?

GF

Just to be clear- Part 25 aircraft are certified and required to be operated such that they will climb the certified amount of gradient under one engine power, under all conditions. To consider only climb gradients for IFR departures and SIDs is folly...a plane that will not fly single engine on a sunny day, is merely being able to see ahead to the scene of the accident.

Another avatar

Have you heard of 3 and 4 engined planes? Presumably, they will not fly far on a single engine.

GF

GF:

Well, three engine birds will if managed properly. I flew two different types for much of my career; 727 and 1011.

The 1011 was an international bird, it had to make with to a landing at an airport after loss of two engines at the ETP. I think the level-off altitude would have been fairly low although I never tried it.:)

Further, every simulator session had an outboard engine fail just above V1 at MGTOW, then as soon as cleaned up and starting en route climb the center engine would always fail. Flew around then dumping fuel to max landing weight followed by a single-engine ILS to landing.

SID departure climb gradient requirements and engine out climb requirements are two totally different requirements.

Engine out requirements certification - Part 25 certification requires different mandatory minimum climb gradients based on segment and number of engines. Example. Part 25 requires that a 2 engine aircraft be able to attain 2.4% gross climb gradient during the second segment climb (gear up to a minimum of 400agl). Second segment climb requirement is in most cases the most restrictive and that is why that number is most commonly used. Also, some aircraft manufactures will extend their second segment to 1500 agl

FAA regulations. FAR s part 121 & 135 now decide how we clear obstacles using the above certification. First, they build in a safety margin by using a lesser climb gradient. For a 2 engine aircraft they use .8% less for a total of 1.6%. This is known as net climb gradient and accounts for the fact the pilot will not perfectly fly the aircraft OEI like during certification. They then say that during all segments a pilot must clear all obstacles in the departure corridor by 35ft. Departure corridor extends laterally 200 ft in airport boundaries and 300 ft from wingtip outside airport boundaries. Once again 2nd segment is usually most restrictive so that is why we usually talk about second segment net climb gradient clearing all obstacles by 35 ft

SID departure climb gradients. One important thing to know is that SID climb gradients are based on aircraft operating normally (all engines operating). Also their climb gradient 200 ft/nm or 3.3 % is a linear climb gradient and not segmented like on part 25 certification and how we actually fly the engine out departure.

Engine out is an emergency procedure and therefore allows us to not not follow the SID. This is where alternate engine out departure created by an airline or 3rd party company are allowed, legal, safe and often used to increase max takeoff weight

Well, three engine birds will if managed properly

Depending on the jurisdiction, if the 3-/4-motor aircraft doesn't have data for two out, it may/will be restricted to 90 minutes. So, for instance, IPEC with their Argosy fleet in Oz had a 90 minute restriction - as I recall, they came up with an AFM change to address that original deficiency.

every simulator session had an outboard engine fail just above V1 at MGTOW, then as soon as cleaned up and starting en route climb the center engine would always fail

AN did the same for the L188 on base checks as the airline didn't have a sim for the Type .. performance on two wasn't overly enthusiastic. Indeed the second failure occurred during second segment once there was enough height for the subsequent descent and reconfiguration.

Similar for the B727 .. never comfortable with the second failure and getting down quite low whilst clawing one's way to (as I recall) 200kt ?

during all segments a pilot must clear all obstacles in the departure corridor by 35ft.

Minor caveat .. 50ft during turns to account for the wing down pod on a four engine bird.

Aterpster

I take your correction; I did some time in the Boeing Tri-motor. It just seemed that the previous poster was too twin -engine oriented the way it was phrased.

GF

As a minor point of interest...second segment isn't always the most restrictive as mentioned above. An example is the ATR with an engne out in icing conditions where the flaps remain at the takeoff position until a higher speed is achieved compared to non-icing conditions, resulting in the 4th segment being most restrictive.

J.T.

As OK465 states, we never lost the second engine until clean, and at least 200 knots.

I can't imagine losing the second engine while still dirty and not buying Farmer Jone's farm.:)

we never lost the second engine until clean, and at least 200 knots

How fortunate .. our deal saw the second one go during the second segment (too long ago to recall actual specifics) .. F/E started dumping like his life depended on it .. nose down, accelerating while the flaps were coming up. Bottomed out around 200 kts as the flaps finished running and then a modest climb.

No-one ever had any major problem in the sim with the exercise.

However, not something to contemplate with a nasty aerodrome.

It is correct, as long as you are within WAT limits and there are no obstacles to consider you are not climb limited! Or are you suggesting that it is allowable to takeoff outside WAT limits?

Which is what I said, as long as the gross flightpath minus 0.8% (=net flightpath) clears all obstacles by 35ft. If it doesn't you will be restricted by a 2nd segment climb (since we are discussing the 2,4% requirement) limited weight. Thus you will be climb limited.

737Jock;
We agree on the substance but are using different terminology. What you call "climb limited" would be "obstacle limited" in my terminology. My apologies for the misunderstanding.

It is correct, as long as you are within WAT limits and there are no obstacles to consider you are not climb limited!

What HazelNuts39 said regarding obstacle limited. The general terminology use is to refer to "climb limited" when citing WAT limited.

Which is what I said, as long as the gross flightpath minus 0.8% (=net flightpath) clears all obstacles by 35ft. If it doesn't you will be restricted by a 2nd segment climb (since we are discussing the 2,4% requirement) limited weight. Thus you will be climb limited.

With respect, good sir, I think you should have a review of the Design and Operating Standards. The 2.4% has naught to do with obstacles and applies as an AFM maximum weight where, and if, limiting.

Because we f;ew the 727 into so many caribean airports with few obstacles but a lot of birds, I asked our check airman to fail two engines at 500 ft on takeoff after we had completed our sim checks and had some time left. I wanted to see if it was possible to clean up before hitting the water since we had no training procedure for that. He initially told me I had to be at 200 knots but he would do it if I wanted to try it.

We got down to 300 feet before we had 200 knots and could climb again but made it by retracting flaps slightly early and using a shallow descent. I thought we might need to get into ground effect to accelerate but we never got that low. We started at V2+10 as in our normal climbs. It gave me confidence that I may not be commited to ditching if it ever happened. If it wasn't working I could still go back to a higher flap setting if ditching was required. Our engineer had to leave so we couldn't dump fuel.

Someone told me Fed Ex trained for this.

Got to disagree with you, if you cannot achieve the required certification climb gradients you are climb limited, if you cannot clear obstacles in the takeoff flight path then you are obstacle limited.

Regardless of the nomenclature on your takeoff charts, these are the limitations. To test it, pick an airport with no obstacles and a long runway, then increase the airport elevation and temperatures until you start to see restricted takeoff weights less than the structural, what do you call these weights? Mr Boeing calls them CLIMB LIMIT weights.

Mutt