2.4% regulatory climb gradient for single engine

[Dariuszw]

I read in one of the posts that multi-engine plane must meet regulatory climb gradient for single engine of 2,4% in order to takeoff. If my single engine performance is less then 2.4% am I not allowed to depart ??? Could someone please elaborate on it.

[safelife]

That is true.

[Intruder]

Maybe... See FAR 25.121(b) for one set of regulations. Where are you, at what point are you measuring, and in what configuration?

[Pugilistic Animus]

I'm guessing that you're referring to second segment performance...what about obstacle clearance or runway geometry limits?:hmm:

[galaxy flyer]

The required gradient varies with number of engines. That is the minimum gradient to meet certification rules and applies even if departing over a cliff and the flight path is over the ocean w/o and obstacle in a thousand miles.

GF

[aterpster]

GF:

The required gradient varies with number of engines. That is the minimum gradient to meet certification rules and applies even if departing over a cliff and the flight path is over the ocean w/o and obstacle in a thousand miles.

It's important to note that the operating rules (U.S. 121.189) require that the certification takeoff flight path (Part 25) be increased as necessary to avoid any obstacle that penetrates the certification surface and cannot be avoided laterally.

Also, there are the gross and net paths.

[galaxy flyer]

Aterpster

No argument there, just posting the certification case. Obstacle clearance is also required, in all cases, not just when a obstacle gradient is published. i.e. 3.3% minimum.

GF

[5LY]

Your runway analysis or performance calculation considers many variables any one of which on a given day on a given runway could be the limiting factor for your t/o. The climb limit is all about your engine out climb capabiltiy. On a twin you are meant to achieve a 2.4% gross or 1.6% net gradient. (numbers are different for 3 & 4 eng. a/c.) The .8 % difference could be the air between you and the rocks if you are climb limited.

SID's are based on a 3.3% climb gradient which is why flying a SID with an engine out is very brave unless your company has assessed the SID to assure that 2.4% will keep you safe. There are companies that do this to simplify their performance calculations, which is fine for them but it muddies the waters for the rest of us as their pilots then will insist that flying the SID with an engine out is safe. It may be for them in their specific op. but it's generally not.

J. T. We need your quiet voice of reason on this.

[mutt]

Aterpster, what do you consider to be the certification takeoff flight path, do you consider it to end at 1500 feet (Note, I know that he is in FAA land :))

Dariuszw How do you account for obstacles in the CitationJet??

Mutt

[Dariuszw]

My obsticle avoidance is accounted by following sids which is official single engine out procedure and no Mutt, Im definitely not in FAA land anymore :( at least not for the last four years. Im in JAA's land now. Anyway, thank you for your answers.

[john_tullamarine]

Some comments -

If my single engine performance is less then 2.4% am I not allowed to depart

Correct with caveats.

If your OEI (presuming you are talking a twin) gradient capability is less than 2.4% (gross) for second segment, then you are above the AFM WAT limit for the conditions and considering operating outside the AFM certification limits.

WAT limits are the limiting gradient requirement to provide some modest climb capability regardless of any other consideration.

unless your company has assessed the SID to assure that 2.4% will keep you safe.

.. or, more likely, has restricted RTOW to provide a profile appropriate to the SID.

but it's generally not

fair comment

[markfly2way]

This is true and I have been turned away for this very reason.

[mutt]

My obsticle avoidance is accounted by following sids which is official single engine out procedure WHAT??????

Can you please supply a reference for this statement, start with your Jeppesen Manual.........

Aterpster is in FAA land...... :)

Mutt

[737Jock]

The aircraft is certified at 2.4% for the 2nd segment. Within its flight envelope it will always make this. This is simple regulations. And you cannot depart outside the aircraft limitations (to which the aircraft was certified) under any normal circumstances.
So the only thing that can be done is finding more performance (new certification), reducing weight or finding a regulator that will allow you to operate outside AFM limits.

The gross flightpath is simply the takeoff flight path that is ACTUALLY flown by the aircraft (starting 35ft above the end of the takeoff distance)

The net flightpath is the gross flightpath minus a mandatory reduction of 0.8% (twin)
The net flightpath ALSO has to clear all obstacles by at least 35ft

The climb limit therefore only arises when the gross flight path minus 0,8% (net flight path) does not clear all obstacles by at least 35ft.

The 0,8% is therefore an extra safety margin (I guess for mishandling) on top of the minimum obstacle clearance of 35ft. It is not the obstacle clearance itself.

[aterpster]

Mutt;

Aterpster, what do you consider to be the certification takeoff flight path, do you consider it to end at 1500 feet (Note, I know that he is in FAA land http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif)

In the abstract of Part 25, I believe it does end at 1,500.

In the real world of 121.189 it ends at 1,500 only if en route climb can be achieved at that point ( 5 s.m. each side of centerline and in en route climb configuration).

Unlike you I am not a performance engineer. :ooh:

[fwagoner]

Does any one know what the "Maximum Takeoff Weight Permitted by Climb Requirements" chart uses for a minumum gradient? I assume this is a single engine chart.

[aterpster]

Mutt:

Can you please supply a reference for this statement, start with your Jeppesen Manual.........

Aterpster is in FAA land...... http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

Mutt, the regulation was changed a couple of years ago to encourage commercial operators to overlay their OEI performance calculations first on the airport's basic obstacle departure procedure ("ODP," used only at light traffic airports) or the applicable SID provided the SID can contain the Part 25 flight path, but using AC 91-121 splays rather than the TERPs splays that were used to design the SID. In such case the SID is the preferred flight path for OEI. Of course, if this assessment of the SID passes OEI muster, then the SID will be so designated by the operator.

In many cases the SID won't work, in which case the game remains unchanged, with one exception. If transition from the SID to a feasible OEI path will not work when an engine fails after takeoff but early in the departure phase the operator is permitted to develop its own departure procedure that will work for both normal (comply with TERPS) and OEI conditions(AC 90-121). This option is not used often and then only when ATC will accept it in advance (usually at lighter traffic airports).

[HazelNuts39]

The maximum TOW limited by climb requirements (WAT limit) for Transport Category Airplanes is based on the most limiting of three T.O. climb requirements with one engine inoperative (gradients for twins):
25.121(a): 0%; Vlof; gear down; T.O. flap, T.O. thrust
25.121(b): 2.4%, V2; gear up; T.O. flap; T.O. thrust
25.121(c): 1.2%; Vfto; gear up; flaps up; M.Cont. thrust

The conditions for these requirements differ in some details from those used to establish the take-off flight path, notably with respect to the variation of thrust with altitude.

The climb limit therefore only arises when the gross flight path minus 0,8% (net flight path) does not clear all obstacles by at least 35ft.
That is not correct. The WAT limits are a certificate limitation and apply regardless of obstacle clearance considerations for all types of operations. Obstacle clearance by the Net TOFP is required by operating regulations such as FAR 121 for Air Carriers.

[aterpster]

Dariuszw:

My obsticle avoidance is accounted by following sids which is official single engine out procedure and no Mutt, Im definitely not in FAA land anymore at least not for the last four years. Im in JAA's land now.

Do you have an authoritative cite that all SIDs in JAA-land are OEI compliant?

[de facto]

Of course he doesnt...:suspect:

[Denti]

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.

[john_tullamarine]

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.

[Pugilistic Animus]

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

:)

[Anotheravatar]

FYI: 737 Jock got it right.

[fwagoner]

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.

[galaxy flyer]

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

GF

[Anotheravatar]

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.

[galaxy flyer]

Another avatar

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

GF

[aterpster]

GF:

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

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.

[frankthefrowner]

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

[john_tullamarine]

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.

[galaxy flyer]

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

[JammedStab]

Second segment climb requirement is in most cases the most restrictive

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.

[aterpster]

J.T.

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 ?

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.:)

[john_tullamarine]

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.

[737Jock]

Quote:
Originally Posted by Jock737
The climb limit therefore only arises when the gross flight path minus 0,8% (net flight path) does not clear all obstacles by at least 35ft.

That is not correct. The WAT limits are a certificate limitation and apply regardless of obstacle clearance considerations for all types of operations.

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?

Obstacle clearance by the Net TOFP is required by operating regulations such as FAR 121 for Air Carriers.

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.

[HazelNuts39]

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.

[john_tullamarine]

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.

[bubbers44]

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.

[mutt]

as long as you are within WAT limits and there are no obstacles to consider you are not climb limited 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

[737Jock]

Ah yes obstacle limited is indeed the correct term.

John, I think you should read my previous post before you sent me to the schoolbenches.

[737Jock]

Yes mutt I mixed up climb with obstacle, i was thinking of it as 2nd segment limited and thought of it as a climb limit which is solely the case for the minimum regulatory climb gradient. When there are obstacles in the 2nd segment requiring a higher gradient it is an obstacle limit.

So I mixed the 2 up.

So what I meant to say is that within the WAT limits the aircraft will always achieve 2,4%.

However I'm not the one stating that the 2,4% regulatory gradient offers a 1,6%
Net flight path. In my view both are completely seperate. One is certifying minimum the other based on the actual performance and weight on the day that considers local obstacles.

[mutt]

aircraft will always achieve 2,4%. I presume you realise that this is an instant value and not a constant value, so you will achieve 2.4% at the start of the climb but it can be less at the end of the 2nd segment.... Surprised? So was I when Mr Boeing stated it :)


Look at far 25.111 and 115 and see if you still think the same thing about the climb gradient.

Mutt

[john_tullamarine]

before you sent me to the schoolbenches

Apologies .. not the point of my comment. The main concern is to avoid the new chums getting confused along the way.


In my view both are completely seperate

Not quite the case. The 2.4% gross data should be viewed as an actual minimum climb capability or even marginally less than that obtained. The 1.6% is the expected gross data reduced by 0.8% to provide a reasonable, real life, margin for obstacle etc., clearance calculations.

Thus, gross approximates what you expect to see on the gauges while climbing out while net is the calculated data upon which one bases the obstacle clear flight profile for preflight calculations.

The two are inextricably linked.


but it can be less at the end of the 2nd segment

Used to cause heartache in Australia where the local rule book required that the performance be maintained throughout the second segment.

[737Jock]

far 25.121 b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in §25.111 but without ground effect, the steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four-engine airplanes, at V2 and with --

(1) The critical engine inoperative, the remaining engines at the takeoff power or thrust available at the time the landing gear is fully retracted, determined under §25.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the airplane reaches a height of 400 feet above the takeoff surface; and

(2) The weight equal to the weight existing when the airplane's landing gear is fully retracted, determined under §25.111.

far 25.117 Compliance with the requirements of §§25.119 and 25.121 must be shown at each weight, altitude, and ambient temperature within the operational limits established for the airplane and with the most unfavorable center of gravity for each configuration.
*

So according to FAR 25 within the WAT limits a 2 engine jet is certified to achieve a steady 2,4% climb gradient.

Can you point me too a reference that says it only momentary?

I'm not sure what you are getting at with Far25.111 and 115. First of all 115 simply defines the takeoff flightpath and nett takeoff flightpath.
111 determines another regulatory climb gradient 1,2%.

FAR 121.189:(a) No person operating a turbine engine powered airplane may take off that airplane at a weight greater than that listed in the Airplane Flight Manual for the elevation of the airport and for the ambient temperature existing at takeoff.

(d) No person operating a turbine engine powered airplane may take off that airplane at a weight greater than that listed in the Airplane Flight Manual --

(2) In the case of an airplane certificated after September 30, 1958 (SR 422A, 422B), that allows a net takeoff flight path that clears all obstacles either by a height of at least 35 feet vertically, or by at least 200 feet horizontally within the airport boundaries and by at least 300 feet horizontally after passing the boundaries.

(e) In determining maximum weights, minimum distances, and flight paths under paragraphs (a) through (d) of this section, correction must be made for the runway to be used, the elevation of the airport, the effective runway gradient, the ambient temperature and wind component at the time of takeoff, and, if operating limitations exist for the minimum distances required for takeoff from wet runways, the runway surface condition (dry or wet). Wet runway distances associated with grooved or porous friction course runways, if provided in the Airplane Flight Manual, may be used only for runways that are grooved or treated with a porous friction course (PFC) overlay, and that the operator determines are designed, constructed, and maintained in a manner acceptable to the Administrator.

(f) For the purposes of this section, it is assumed that the airplane is not banked before reaching a height of 50 feet, as shown by the takeoff path or net takeoff flight path data (as appropriate) in the Airplane Flight Manual, and thereafter that the maximum bank is not more than 15 degrees.

(g) For the purposes of this section the terms, takeoff distance, takeoff run, net takeoff flight path and takeoff path have the same meanings as set forth in the rules under which the airplane was certificated.

So 189 (a) determines amongst others the certified climb limit weights determind during certification.
And 189 (d) determines obstacle limited weights/climb gradients.

The 0,8% penalty is just for defining the net takeoff flightpath and is used during obstacle climb limit determination. Not performance climb limit determination.

[737Jock]

I agree that any obstacles penetrating the 35ft obstacle clearance on a net takeoff path of 1,6% will lead to a higher required net takeoff path and thus gross takeoff path.

But this is a far 121.189 Operator requirement not a far25 certifying requirement like the 2,4% gradient.

In that sense the 1,6% figure is irrelevant, because as operators we need to take the actual obstacles into account and assure that the net path clears them by 35ft.( 121.189 d) We don't do this by starting of at 2,4%. It is done by taking all relevant obstacles into account, add 35 feet, determine the net path. Then add the penalty and thus determine the gross flightpath required. This could be 2%, 3% 5% etc...
For all these percentages you could make a specific WAT table that determines the limiting weight.

If there are no obstacles we are still limited by certifying limits (121.189a) like the 2,4% 2nd segment WAT limit (or required groos obstacle climb gradient is less than the certifying limit)

[john_tullamarine]

But this is a far 121.189 Operator requirement not a far25 certifying requirement like the 2,4% gradient.

One needs to keep in mind that second segment WAT is 2.4% and not related to nett. However, whatever gross is required for obstacle or other operational need is then linked to a net capability 0.8% less. Put it down to minor emphasis in meaning.


WAT limits ... a steady 2,4% climb gradient. Can you point me too a reference that says it only momentary?

The physics of the matter is the reference.

As soon at the ambient conditions (Hp/OAT) vary, the steady climb performance will vary ergo the gradient may reduce through the climb. To satisfy yourself on this one, have a look at any WAT chart with different entry arguments.

The reference to steady is to preclude enterprising things, such as a bit of zooming, etc.

Necessary, also, to keep in mind that the regs can't be read in isolation. One needs to review ACs, policy letters and the like to get a story which, itself, varies over the years .. hence one Type will have different rules applied compared to another.

[737Jock]

Hi John

I edited my post above. I simply make a clear distinction between what we as operators should do far121.189 and what the certifying manufacturer should do far25.

Off course they are linked, but as long as we stay within AFM limits the aircraft will perform to its certified limits ie. 2nd segment 2,4% WAT. As you said it is not related to net and thus not to obstacles.

For us as pilots the important things are to not bust AFM LIMITS like 2,4% WAT in 2nd segment. And ensure the net takeoff path clears all obstacles by 35ft by ensuring the aircraft is not too heavy to achieve the required gross path.

The mentioned 1,6% over complicates this and is simply not relevant. In fact it is only relevant where obstacles determine that exactly a 1,6% net path is required. But this is determined by obstacles not certifying limits and would be a pure coincidence.

In other words we check what climb gradient is required based on obstacles and AFM limits and take the highest to determine our limited weight.

[john_tullamarine]

Time for us to go have a beer, methinks..

[737Jock]

Haha I wish... Not for another few hours

[Zeffy]

737Jock
In other words we check what climb gradient is required based on obstacles and AFM limits and take the highest to determine our limited weight.

No.

Pilots don't have the requisite obstacle data to perform those calculations.

Part 25 instructs the manufacturers on the weight limits and performance data that must be provided in AFM's.

In FAA-land, 121.189 is the operating regulation.

AC 120-91 (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%20120-91/$FILE/AC120-91.pdf) describes how operators can comply with 121.189. It also makes clear that TERPS and OEI operations are not the same.

The calculations are far too complex for pilots who are not performance engineers. :)

[john_tullamarine]

The calculations are far too complex for pilots who are not performance engineers

Not really the case .. and the AFM leads one by the hand in any case.

Having detailed and accurate obstacle data is the problem .. which is why pilot calculations generally are based on simplified data appropriate to obstacle clear surface data.

[Zeffy]

Not really the case .. and the AFM leads one by the hand in any case.

Easy for you to say, jt... :)

Having detailed and accurate obstacle data is the problem .. which is why pilot calculations generally are based on simplified data appropriate to obstacle clear surface data.

Oh, I'd agree that most pilots could find the WAT limits if there were no obstacles in the regulatory departure corridor.

I'm only suggesting that if one gave a reasonably complex departure problem with both close-in and distant obstacles -- one that would introduce thrust time limits and selections of clean-up heights -- to 100 line pilots, it would be surprising if not impossible to find more than five correct answers to the question of "what is the maximum allowable TOW?"

[737Jock]

Ok I let something do it for me, it is called a computer. And what I said is exactly what it does.

Btw I'm in jaa/easa-land.

[Zeffy]

Ok I let something do it for me, it is called a computer. And what I said is exactly what it does.

Please help me understand.

Does the "computer" have obstacle data for each runway? If so, how is the obstacle database updated?

Thanks,

Z

[john_tullamarine]

a reasonably complex departure problem with both close-in and distant obstacles

Generally, the pilot doesn't have the time to run a detailed calculation during line operations.

The traditional method used in Oz works OK -

(a) the aerodrome owner publishes runway distance and obstacle clear splay data

(b) the operator publishes a simplified set of performance data which is suited to runway distance and obstacle clear gradient calculations. This can be in a variety of presentations but none is too difficult for Government work.

We occasionally used this sort of stuff on the line, generally when a NOTAM or similar temporarily invalidated the normal company RTOW data for a runway. The general caveat is that the technique is restricted to simple straight ahead departures.

[Zeffy]

Thanks for the explanation, jt. :ok:

[737Jock]

Yes it does. The computer is updated every 2 weeks /every month or so. It even gets modified for Notams, and has specified engine out procedures for each runway.

In addition you can add obstacles yourself. Reduce runway length at begin or end, adjust for 90 degree or 180 degree lineup etc etc etc And do multiple runway calculations at the same time. And off course it has all usable intersections for departure listed as well.

Oh and off course you can add all kinds of performance affecting MEL and CDL items.

The laptop is called LPC for airbus (my username is a bit outdated;) and the software FOVE.

It also does W&B landing perf dispatch and inflight and offcourse contaminated runway perf. Again all with MEL/CDL integration.

[Zeffy]

Thanks, 737Jock.

I had begun to visualize pilots poring over charts, graphs and obstacle data... hence my comment that pilots aren't capable of making the requisite calculations.

My apologies for sound so patronizing; I appreciate your taking the time to describe LPC/FOVE.

[4dogs]

737Jock,

Can you point me too a reference that says it only momentary?

I think you chose to emphasise the wrong part of the regulation. :=

far 25.121 b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in §25.111 but without ground effect, the steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four-engine airplanes, at V2 and with --

The point at which the performance must be demonstrated is emphasised, the nature of the performance must be steady and not as a result of any temporary trickery like zooming/speed bleed, ground effect, etc., but there is nothing that says it must have the same value at the end of the path as it did at the beginning. :cool:

Stay Alive,

[737Jock]

far 25.121 b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in §25.111 but without ground effect, the steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four-engine airplanes, at V2 and with --

:ugh: you might want to read john's reply explaining why the 2,4% can vary. This is definitely not the correct answer.

The point at which the performance must be demonstrated is emphasised
No the configuration in which the performance must be demonstrated is emphasised.

[Skky]

OK... Ill toss a grenade into this campfire...

FAR 23 and 25 are CERTIFICATION standards... The manufacturer (not the pilot) is responsible for certifying the aircraft therefor these regulations are applicable to someone wanting to obtain or change the type design of the aircraft.

Sec. 25.1
Applicability.
(a) This part prescribes airworthiness standards for the issue of type certificates, and changes to those certificates, for transport category airplanes.
(b) Each person who applies under Part 21 [New] for such a certificate or change must show compliance with the applicable requirements in this part.

Part 25 aircraft are not allowed the use of TR's, must have brakes worn to limits, and have an Engine Failure Recognition time built into performance calculations. Does this mean pilots are not allowed to use TRs, should always have worn brakes, and wait 2 seconds after Vef to initiate an abort? Of course not...
Remember that when the FAA determines a new aircraft complies with ALL of Part 25, it is issued a Type Certificate. As long as the aircraft continues to meet requirements of the TC, it complies with Part 25 (among others) and the Airworthiness Certificate is valid. It is not up to the pilots to ensure compliance with 25.903, 33.76 or 25.1455 any more than it is their responsibility to ensure compliance with 25.121. The aircraft met the requirements when it was certified and WAT conditions will not invalidate an Airworthiness Certificate.



Aircraft Certification and Climb requirements
During certification, Part 25 only requires that manufacturers establish weights, altitudes and temperatures (WAT) that produce particular climb gradients (see Part 25.111, 25.115, and 25.121) and publish that data in the AFM (it would require about 5 pages). However, I have hundreds of pages of WAT data for climb gradients ranging from 0.0% 2nd segment OEI to as high as 14% using weights lighter that my BEW (9% is about the most realistic number I can achieve OEI). Why are they publishing such wide ranging data? Because there is no regulatory requirement that an aircraft actually have a 2.4% climb gradient (or any other gradient) under every possible WAT combination when it comes on off the production line (its physically impossible). The minimum legal climb gradients that a pilot will be required to meet will be established by a number of variables ranging from OpSpecs to country of registration.

All US registered aircraft must meet the applicable requirements of Part 91 unless they are subject more stringent regulation. Turbojet aircraft are no exception. An interesting point is that under Part 91, there are no regulations that require climb requirements above 35' be calculated by a pilot (91.605). While WAT were established during aircraft certification that produced particular gradients, the aircraft does not have to be operated at those WATs. As long as there is approved data in the AFM (again, I have data for 0.0% 2nd segment OEI operation) and you do not exceed a published limitation in the AFM, you are legal for a Part 91 flight.



Accept a departure procedure or instrument approach (MACG), operate under 121, 135, 125 or just want to physically climb over anything taller than a lake with OEI and it gets more complicated.. Legal does not mean safe.


SIDS and DPs
I think this was in some earlier posts but if you accept a departure procedure, you are expected to maintain the appropriate climb gradient – all engines operating. Does your acft manufacturer publish all engines operating climb data? Mine does not, so (if yours does, skip ahead) how does one know if they will meet the climb requirements without a AFM data. You don’t….
You will not find anything in the regulations or AFMs that allows you to use OEI data to calculate all engine operating climb gradient. Would your Check Airman let you use a flaps 12 table to calculate a flaps 20 take off?. Of course not...

As logical as the argument may be, it isn’t legal (remember, Safe does not mean Legal).
FYI - There have been some ALJ decisions and FSIM guidance that is slowly changing this but, as of now, this is what we have.


Engine Failure
Lose an engine at V1 and what are you legally required to do under Part 91? Assuming you have decided you have an emergency? Nothing.
Hopefully you have made some calculations with regards to the laws of physics but TERPS, FARs and AFMs do not trump Emergency authority. Climb at 0.0 westbound across the Pacific until you have burned off fuel – that’s legal. Legal does not mean safe.



That should be enough dynamite in the campfire for one night.. I welcome your input and the references that go with it.

[FE Hoppy]

Skky, If you believe you can legally operate at less than the certified limits simply because data outside those limits is included in your AFM I'm afraid you are mistaken.



Not so much a grenade as a big fat cream pie.

[HazelNuts39]

The aircraft met the requirements when it was certified and WAT conditions will not invalidate an Airworthiness Certificate.
The Airworthiness Certificate states that the airplane must be operated in accordance with the Limitations stated in the Airplane Flight Manual. These limitations include structural limits (MTOW, MLW, MZFW), CG limits, max operating speeds, and WAT limits.

Sec. 91.9 Civil aircraft flight manual, marking, and placard requirements.
(a) Except as provided in paragraph (d) of this section, no person may operate a civil aircraft without complying with the operating limitations specified in the approved Airplane or Rotorcraft Flight Manual, markings, and placards, or as otherwise prescribed by the certificating authority of the country of registry.

[chrislikesblue]

I was told by a captain that the FMC of the aircraft (B737) calculates the performance of the aircraft on the SID for one engine out event when you enter the SID. Can someone confirm this? I was not able to find any reference to support this statement so I am not sure if this is correct.

[john_tullamarine]

If I might emphasise the comments of intervening posters ..


It is not up to the pilots to ensure compliance with 25.903, 33.76 or 25.1455 any more than it is their responsibility to ensure compliance with 25.121. The aircraft met the requirements when it was certified and WAT conditions will not invalidate an Airworthiness Certificate.

Of course not .. however, it IS up to the pilot to ensure that the aeroplane is operated in a manner which is not inconsistent with the Standards embodied in the design (eg Part 25).


The minimum legal climb gradients that a pilot will be required to meet will be established by a number of variables ranging from OpSpecs to country of registration.

.. and that will be the page in the AFM which details the WAT limits.


As long as there is approved data in the AFM (again, I have data for 0.0% 2nd segment OEI operation) and you do not exceed a published limitation in the AFM, you are legal for a Part 91 flight.

That may be the case (my bolding, above) but there will be another chart which gives the WAT limits .. the how-to-use-it data will indicate that the WAT limit comes first then the other stuff ie, if the second segment charts have data apparently below the WAT limit, that will be for interpolation or similar reasons ..


Climb at 0.0 westbound across the Pacific until you have burned off fuel – that’s legal

That would be constrained by operating rules rather than design rules. However, why would one wish to do that when the aircraft should be quite capable of climbing as per the normal segmented flight path (I presume we are talking heavies) ?


I was told by a captain that the FMC ..

No reason why one couldn't set up such an animal. The sums are fine for the least capable PC .. However, the database amendment workload would escalate dramatically.

I suggest that a more reasonable expectation (unless you have documented evidence to the contrary ..) is that the box will tell you what you can expect to see OEI depending on the weight, Hp, OAT it thinks exists .. but with NIL consideration of any specific terrain .. including SIDs.

[FlightPathOBN]

to add to JT's post..

There is nothing in the design criteria that addresses EO. It is considered an emergency op. Nothing in charts(unless you had them privately designed) will reference EO.

I was told by a captain that the FMC of the aircraft (B737) calculates the performance of the aircraft on the SID for one engine out event when you enter the SID. Can someone confirm this?

That is not true. There are no EO DP procedures unless you had one customed designed.

You will find that for twins, if you actually calc it out, that there is virtually no way you can meet SID requirements EO, or missed EO in gradient, unless you have a special procedure designed, or limit your weights.

again, I have data for 0.0% 2nd segment OEI operation)

if you are EO, you dont have a level off 2nd segment.

Again, nothing in procedure design criteria references EO, either in missed or departure.

[galaxy flyer]

FPO

For some strange, inexplicable reason, I think he is referring a second segment "climb" of 0.0%, that is zero climb.

GF

[Skky]

@FE Hoppy – I’m not sure I understand what you asked/stated but if you are not limited by the AFM or regulation, then it is legal. Data will not be in the AFM unless it is approved during the type certification process which is done in compliance with Part 23/25.

(*AFMs may actually have unapproved data but it must be clearly notated. For example, I have overweight landing Vref speeds but that does not authorize me to plan overweight landings.)

@HazelNutz39 – there is no requirement in Part 25 that a manufacturer provide operational data that exceeds any particular climb gradient. Certification rules (Part 25) say that the manufacturer will provide each WAT within the operational limits of the aircraft that produce a climb gradient of 2.4% OEI (two engine acft). In other words, it’s not contrary to Part 25 for manufacturers to publish a WAT for a 0.4% second segment OEI climb, nor is it contrary to provide data for a 14% second segment OEI climb.
I completely agree, you must comply with what is in the AFM (FAR 91.9) and MTOW, altitude limitations, temp limits (min and max), CG limits, Vne ect. Remember that performance charts are the laws of physics – simplified. If you configure an aircraft as per any performance chart, the aircraft CANT do anything else but deliver the numbers in the book.
As for 91.605, I agree you cant depart an airport that you don’t have performance data for (or is prohibited by the AFM), but Part 91 does not specify climb gradients after 35’. I other words, I am in compliance (legal), if I have a WAT in my AFM for 0.4% OEI climb, and I can legally depart. Consider the implications of 25.117.


@john_tullamarine I agree, the AFM is created for the sole purpose of ensuring that the design limitations are clearly outlined. FAR 91.9 then elevates the guidance in the AFM to that equal to a regulation. There will not be anything in an AFM that is contrary to a certification regulation (the FAA will not approve it).
AFMs do not specifically require a minimum climb gradient. Every AFM will have the data required by FAR25.121 and most will have more data but no AFM will have less. If you need a particular OEI gradient, the performance section will tell you what WAT will give you your requested climb performance. The OEI climb performance you require may be due to TERPS, OpSpecs, 121/135 regulation, DP, noise or JAA/CAA. If in the course of trying to obtain the desired climb performance, you “run off the chart” or data is not provided for your desired OEI climb then, yes, you must find another way. You are allowed to interpolate but cannot extrapolate.
I am interested as to what the lowest OEI climb gradient is published in your AFM. MGTOW, 40C and 4200 msl will result in 0.0% OEI climb in mine.


@FlightPathOBN – FAR 23 and 25 are aircraft design certification requirements and FAR 25.121 is titled Climb: One- Engine Inoperative. All most all of my climb charts are OEI (in fact all engine operating charts are the issue). There are several companies out there specializing in custom departure procedures (and they are affordable). We reference them for 90% of our take offs and brief the alternate departure procedures in about 25% of our operations. We meet the SID climbs with OEI the rest of the time. As for MACG, we don’t often calculate that (but we should) and we have procedures to adjust our mins so that we can meet a MACG in places where it becomes critical (ASE in the summer for example).

[galaxy flyer]

The plane MUST be operated within its certification rules which includes the WAT limit of 2.4% climb gradient to a minimum of 400' AFE. You cannot blow off the certification standards by saying you are FAR 91.

GF

[FlightPathOBN]

Skky,

There are several companies out there specializing in custom departure procedures (and they are affordable).
hmmmm...my favorite to use is a company called Operations Based Navigation (http://operationsbasednavigation.com/)!

There are only a few airlines which have OEI procedures in the FMC, and they have been associated with RNP procedure designs. There is one for Burbank, so they didnt have to limit weights on hot days...
and I am glad that you realize that SID, or the missed approach on a plate is not OEI.
I mean you could use them, as long as you calc out OEI performance with temp, and unload the aircraft!

[4dogs]

Skyy,

Are you talking about private operations in something like a Global Express? :confused:

Stay Alive,

[Skky]

@4dogs – Yes.. Part 91 operations in a jet aircraft


@FlightPlathOBN – I use Aircraft Performance Group Welcome to Aircraft Performance Group (http://apg.aero/MW/) They can do runway perf for any airport (they haven’t failed me yet).. they just need your aircraft loaded into their database. They often use the same flight path as the published Departure Procedure but because their lateral clearance is less than TERPS, you can depart heavier (that will start another conversation I'm sure). The advantage is you already have it in your FMS. When they provide a completely new procedure, it is not too difficult to plan/program into an FMS. We have company procedures that outline how this is done.
Its not so much of a “realization” as it is just reading it. TERPS says quite clearly that it is not OEI. Furthermore OEI is an Emergency (at least in my book) and continuing on a DP and trying to meet a climb requirement when there is a perfectly viable escape route available is – in my book – the very definition of careless and reckless.
You are exactly right, about offloading… If I may paraphrase the whole thing, you essentially need a “Plan B” to be legal. Plan B may be an escape procedure, it may be flying the DP at a weight that allows you to meet the climb requirements OEI, or it may be fly over the ocean until you can climb high enough to turn around. As long as you can prove your “Plan B” is viable (and you can climb to 35’), you are legal. Many operators choose to offload in order to comply with the DP OEI. Nothing wrong with that – other than you may not have actually been required to do that (again, from a purely legal perspective). (and I’m sure you meant Landing Climb).


@galaxy flyer – can you show me where in the regulations (Part 91 operation) where it says a pilot must operate an aircraft with a 2.4% to 400”? Psalm and verse if you please.


Thanks

[HazelNuts39]

The plane MUST be operated within its certification rules which includes the WAT limit of 2.4% climb gradient to a minimum of 400' AFE.Correct, except that the climb gradient of 2.4% is for the "thrust available at the time the landing gear is fully retracted". Since thrust reduces with altitude, the gradient at 400' is usually somewhat less than 2.4%. The WAT limit requirements of 25.121 are related to, but also distinct from the takeoff path requirements of 25.111.

Skky is probably a 'troll' who knows perfectly well that it's illegal to operate an airplane outside its operating limitations.

[mutt]

herewith is your psalm and verse.... FAR 25.121 Airworthiness

(b) Takeoff; landing gear retracted. In the takeoff configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in §25.111 but without ground effect:

(1) The steady gradient of climb may not be less than 2.4 percent for two-engine airplanes, 2.7 percent for three-engine airplanes, and 3.0 percent for four-engine airplanes, at V2with:

Mutt

[mutt]

You also have to comply with ICAO annex 6, part 2, chapter 5, as the USA didn't file any differences.

Mutt

[aterpster]

Mutt:

herewith is your psalm and verse.... FAR 25.121 Airworthiness

In the U.S. that transfers to the applicable commercial flight operations regulations. But, for the non-commercial operator flying a Part 25 aircraft it does not. Part 91 does require the non-commercial operator to calculate the balanced field for takeoff but once airborne there is no specific requirement to make good the Part 25 takeoff flight path, all engines operating or OEI. With all engines operating he is bound, though, by a SID climb gradient as I would be in my Part 23 bugsmasher.

[FlightPathOBN]

Skky,

Thanks for the link. Interesting app. for the smaller ac...

[galaxy flyer]

Ok, skyy, your point might be true, BUT why would any responsible operator of Part 25 aircraft NOT try to achieve the highest standards by using appropriate runway analysis for departure? We, and a number of operators, use APG or equal on all departures.

GF

[BizJetJock]

Part 91 requires you to operate in accordance with the flight manual limitations.

Below is a typical AFM from a Part 25 a/c.

2. MAXIMUM ALLOWABLE TAKE-OFF WEIGHT
The maximum allowable take-off weight is limited by the most restrictive of the following:
• Maximum approved take-off weight
(Refer to Chapter 2; LIMITATIONS – STRUCTURAL WEIGHT),
• Runway length available,
• Climb requirements,
• Obstacle clearance requirements,
(First, verify if the second segment of the take−off flight path extends beyond a pressure
height of 1,500 feet above the airport and consider if potential adjustments are to be made.)
• Maximum demonstrated brake energy,
• Maximum tire speed,
• Wheel brake cooling limitations
(Refer to PERFORMANCE – TURN-AROUND TIME – Cooling of Wheels, Brakes and Tires,
in this chapter).

Note that obstacles are in there as well.

It seems pretty unequivocal to me - which bit of Maximum Allowable Takeoff Weight do people have a problem with? :ugh:


Apart from the legal considerations, why would anyone not want to take the climb performance into account? A 2.4% gradient with no obstacles or 35 feet clearance if there is seems pretty sphincter tightening to me:sad:

Added to which, in my book I'm being paid to keep the boss safe - and he thinks so too. He would probably be mightily unimpressed (= me fired) if he though I was gambling with his and his family's safety.

[HazelNuts39]

which bit of Maximum Allowable Takeoff Weight do people have a problem with?Two bits actually:

- Climb requirements: The maximum takeoff weight limited by climb requirements, commonly referred to as WAT-limit, provides a gradient of not less than 2.4% for twins at the point where the landing gear is fully retracted, OEI. It is an operating limitation under Part 91, except for Skky.

- Obstacle clearance requirements: Obstacle clearance is not a certification requirement. The certification requires that the AFM provides information on the Net flight path, and FAR part 121 requires its use to ensure obstacle clearance, but Part 91 does not.

FAR Sec. 25.1533

Additional operating limitations.

(a) Additional operating limitations must be established as follows:
(1) The maximum takeoff weights must be established as the weights at which compliance is shown with the applicable provisions of this part (including the takeoff climb provisions of Sec. 25.121(a) through (c), for altitudes and ambient temperatures.
(2) (...)

[aterpster]

Bizjetjock:

Added to which, in my book I'm being paid to keep the boss safe - and he thinks so too. He would probably be mightily unimpressed (= me fired) if he though I was gambling with his and his family's safety.

Then, he doesn't mind paying a professional performance and engineering company to do a full assessment for each runway you use, including an OEI flight path. Unfortunately, not everyone sees the value of such a service.

[mutt]

Unfortunately, not everyone sees the value of such a service. But more and more operators are starting to see that value. Skky's reading of FAR91 might be correct, but the interpretation is not. Why is it that the Honeywell FMS has WAT climb limits under FAR91, surely if it wasn't required, Honeywell wouldn't have invested the money into validating the data?

Mutt

[aterpster]

mutt:

But more and more operators are starting to see that value. Skky's reading of FAR91 might be correct, but the interpretation is not. Why is it that the Honeywell FMS has WAT climb limits under FAR91, surely if it wasn't required, Honeywell wouldn't have invested the money into validating the data?

When Honeywell designs a system, say for a Falcon 900EX or G550, they do not know whether the operator will be Part 91, 121, or 135.

There is no FAR 121.189 equivalent in Part 91. If the AFM made the flight path necessary for all Part 25 airplanes operated by U.S. operators then there would be no need or reason for 121.189 (or its Part 135 equivalent).

[galaxy flyer]

I think BizJetJock has it precisely correct. FAR 91 requires compliance with AFM limitations; FAR 25 AFMs require OEI climb out flight paths, hence you must meet the paths, by some means. I read thru the AFMs of the three types I'm familiar with and they all say pretty much what he posted.

GF

[Zeffy]

Subpart G—Additional Equipment and Operating Requirements for Large and Transport Category Aircraft

§ 91.605 Transport category civil airplane weight limitations.

(a) No person may take off any transport category airplane (other than a turbine-engine-powered airplane certificated after September 30, 1958) unless—

(1) The takeoff weight does not exceed the authorized maximum takeoff weight for the elevation of the airport of takeoff;

(2) The elevation of the airport of takeoff is within the altitude range for which maximum takeoff weights have been determined;
...
...
...

(c) No person may take off a turbine-engine-powered transport category airplane certificated after August 29, 1959, unless, in addition to the requirements of paragraph (b) of this section—

(1) The accelerate-stop distance is no greater than the length of the runway plus the length of the stopway (if present); and

(2) The takeoff distance is no greater than the length of the runway plus the length of the clearway (if present); and

(3) The takeoff run is no greater than the length of the runway.

[Pugilistic Animus]

It is probably more economical to hire a performance companythan it is to back off the weight to meet the DP gradients OEI

However although not explicitly written in part 91 I can almost guarantee that if an incident occured...and you got too close to an obstacle for a near CFIT...they'd nail you with a 91.13

[Zeffy]

However although not explicitly written in part 91 I can almost guarantee that if an incident occured...and you got too close to an obstacle for a near CFIT...they'd nail you with a 91.13

When has that ever happened?

Got a cite?

NTSB Adjudication?

Or not really a "guarantee"?

[FlightPathOBN]

PA,

You must fly out of TEB!
That is why Sulley decided to land in the Hudson than divert to TEB, he didnt want an OEI 91.13 violation!

[Pugilistic Animus]

I'm writing from my phone again...so please excuse me

ZEFFY...the DOT is the worst of all government beauracracies...so if the FAA can find a reason for enforcement they will...although i can think of any enforcements as described...when i read some other action taken by the faa i just would be surprised...so it's just my best guess at what they may do...but i wouldn't chance...i think 91 operators should at least try to make the DP oei...just sounds responsible to me..

FPOBN...I have not seen TEB since 07 iirc....but Im not sure what you mean regarding sully???....:-)

[mutt]

Considering that FAR91 was written for FAR 23 and FAR 25 aircraft, it stands to reason that they didn't cite climb gradients, however for those of us operating FAR 25 large aircraft, with safety management systems, safety factors, oversight authorities, noise requirements and SAFA, we cannot operate as per the letter of FAR91, it just isn't acceptable. We have takeoff performance issues with SAFA while in full compliance with FAR121 :)

Sully means Captain Chesley `Sully' Sullenberger III, the Captain of U.S. Airways Flight 1549.

Mutt

[Zeffy]

..i think 91 operators should at least try to make the DP oei...just sounds responsible to me..

Far more responsible would be to engage the services of a profession performance engineering company whose runway analysis products are compliant with AC 120-91 (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%20120-91/$FILE/AC120-91.pdf).

With respect to the opinion that "making the DP OEI" would be a good idea, what would the advocate of such a solution propose to do at KLAS on the COWBY4 SID?

http://i202.photobucket.com/albums/aa92/zeffy_bucket/COWBY4.png

http://i202.photobucket.com/albums/aa92/zeffy_bucket/COWBY4zoom.png

`


As indicated by this recent article published by NBAA (http://www.nbaa.org/ops/safety/climb-performance/20120510-one-engine-inoperative-climb-performance-planning.php), numerous problems arise when an operator attempts to apply AFM data to a SID or ODP -- e.g., failure to consider low, close-in obstacles and invalid calculations due to time limits on takeoff thrust, etc.

[kellykelpie]

I find Pprune can be a very interesting resource at times and this thread certainly proves it. It's great to have such a broad knowledge base - thanks to J.T for explaining what I consider a complex subject.

[aterpster]

P.A.:

However although not explicitly written in part 91 I can almost guarantee that if an incident occured...and you got too close to an obstacle for a near CFIT...they'd nail you with a 91.13

How would the feds know that someone got "too close" to an obstacle?

And, are you speaking of all engines operating or OEI?

[aterpster]

Mutt:

Considering that FAR91 was written for FAR 23 and FAR 25 aircraft, it stands to reason that they didn't cite climb gradients, however for those of us operating FAR 25 large aircraft, with safety management systems, safety factors, oversight authorities, noise requirements and SAFA, we cannot operate as per the letter of FAR91, it just isn't acceptable. We have takeoff performance issues with SAFA while in full compliance with FAR121 http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

The standard of care in the performance arena required from a regulatory standpoint is simply different for commercial and private flight operations. And, you are right, even with Part 121 operators who meet the minimum standards set forth in 121.189 can easily have a CFIT with OEI. The industry has been spared most of this in the turbine era because of the fantastic reliability of the powerplants.

[aterpster]

For many years the FAA would not permit commercial operators to make IFR takeoffs on Runway 18 at South Lake Tahoe, California. (KTVL). A few years ago a different "performance" decision was made by the FAA. Below are today's takeoff minimums and ODP (obstacle departure procedure) for KTVL.

The takeoff minimums notwithstanding, a compliant takeoff flight path analysis is weather independent. I wonder how even the best takeoff performance engineering company could provide a safe takeoff flight path for this runway. The splays recommended in AC 120-91 would limit payload considerably more than application of the minimum requirements of FAR 121.189. But, a minimum 121.189 path would likely result in a OEI CFIT crash. Or does the modern performance engineer provide an RNAV track that is somewhere between the minimum requirements of 121.189 and the splays of AC 120-91. And, even applying the splays of AC 120-91 is containment assured without positive course guidance out of this canyon?


http://i201.photobucket.com/albums/aa214/aterpster/KTVL.jpg

[mutt]

Zeffy...... under 121, we would go straight ahead and account for the obstacles in the flight path, if we didnt get sufficient operational weight doing that, we would design a single engine flight path to avoid limiting obstacles.... we wouldnt attempt to follow the SID with an engine out as the payload would be too severely penalised.

Mutt

[Zeffy]

Mutt - thanks.

Actually, I wasn't advocating flying a SID OEI -- just pointing out the impracticality with the KLAS example.

Due to misinformation promulgated by FAA Part 142 training outfits over the years, many corporate operators have been lead to believe that they need to be able to fly a SID/ODP following the loss of an engine. Simply not true.

[mutt]

aterpster, how about "immediate right turn at DER to SHOLE and hold, max speed in turn 160 KIAS".

But based on the noise restrictions, we wouldn't be allowed in there anyway :)

Mutt

[aterpster]

mutt:

aterpster, how about "immediate right turn at DER to SHOLE and hold, max speed in turn 160 KIAS".

I don't think so. :) Check the topo.

Runway 36 is the calm wind runway. In fact, the airport manager recommends 36 so long as tail wind limitations aren't exceeded.

http://i201.photobucket.com/albums/aa214/aterpster/KTVLTopo.jpg

[mutt]

[img]http://farm9.staticflickr.com/8165/7685613988_629549fcfd_z.jpg (http://www.flickr.com/photos/pprunemutt/7685613988/)


Oops, thats the problem of only using Jeppesen for my guesses!

I cant read the heights on the Topo, but it looks like 6900 feet for twin peaks, so that would be an obstacle measured from the adjusted runway end. Then it would depend on how much of an impact it had on the takeoff weight. If the impact was too severe, then i would add the 6400 feet obstacle straight ahead, and define a turning point back to the right that would increase the track distance to the 6900 feet point.

Almost forgot, as i operate under FAR91, all that i legally have to do it look at the obstacle, decide that i can clear it, and yee haw, advance the power :)


Mutt

[FlightPathOBN]

"SHOLE"?!?!

Is that pronounced "ESS-HOLE"?

"Ess-HO"

"show-LEI"?

"shhh- OLE'!"

I can just imagine....

(sorry for the interruption)

[aterpster]

Mutt:

Oops, thats the problem of only using Jeppesen for my guesses!

I cant read the heights on the Topo, but it looks like 6900 feet for twin peaks, so that would be an obstacle measured from the adjusted runway end. Then it would depend on how much of an impact it had on the takeoff weight. If the impact was too severe, then i would add the 6400 feet obstacle straight ahead, and define a turning point back to the right that would increase the track distance to the 6900 feet point.[/quote]

The twin peaks are 6,900, plus vegetation. The ridge line to the west is 7,200, plus vegetation. Byond the 7,200' ridge line is a small lake then the terrain slopes up quite rapidly to almost 10,000.


Almost forgot, as i operate under FAR91, all that i legally have to do it look at the obstacle, decide that i can clear it, and yee haw, advance the power http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

Exactly!

[Pugilistic Animus]

How would the feds know that someone got "too close" to an obstacle?

And, are you speaking of all engines operating or OEI?
Aterpster

ratted out by ATC (Radar)...exclaim over the radio that you were almost killed, something like that...and don't think filing an ASR is fully protective, I know that they have ways to get you despite filing one...:)

'OEI'

Zeffy
Far more responsible would be to engage the services of a profession performance engineering company whose runway analysis products are compliant with AC 120-91 (http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/list/AC%20120-91/$FILE/AC120-91.pdf).

I agree wholeheartedly :ok:

With respect to the opinion that "making the DP OEI" would be a good idea, what would the advocate of such a solution propose to do at KLAS on the COWBY4 SID?


Reduce the weight till I make the most limiting gradient, at least it's something proactive ..and frankly I don't care about engine time limitations; it's not as if the thing is just gonna explode ( I hope):}...but, I'm not reducing to MCT until I'm sure,...but yeah but that would be a long long climb..you'd definitely can't pretend that's a real OEI procedure that's for sure :\:\:\.....let'em boroscope the engine far cheaper than slamming into a mountain.... yes, I do understand the many differences between a real NTOFP and a DP...:)

Some FAR 23 jets also use FAR 25 net flight path data, kind of a mixed bag certification...and have the published data...I actually found an interesting article on that particular topic but I can't seem to find it now, if I do I'll link it...

Sully means Captain Chesley `Sully' Sullenberger III, the Captain of U.S. Airways Flight 1549.


Mutt I know I just wasn't sure how 91.13 plays into it...in fact I learned a great lesson from 'Sully' in that you can't go to the birds to get the answers...:}
.Although I respect Sully, my real 'heroes' wrt to miracles are Al Haynes and his crew and that DHL Airbus crew:\:\:\

all I do nowadays is show folks how to fly little baby planes-part time... I'm no longer current in anything, and not very 'experienced' comparatively, so I really don't worry anymore about these things, I always used let the captain worry anyway:ouch:...this markets really sucks, airlines suck... don't wanna fly regional...rather teach...I guess:)