Approach Climb Gradient

SpeedWeasel · Post by **SpeedWeasel** » Thu Mar 25, 2004 11:23 am

I know that for a commercially operated, twin engine, turbo-jet aircraft to depart an airport IFR, the aircraft must be able to maintain the second segment climb performance required by the SID with an engine out.

Does this also mean the same aircraft must be able to meet these requirements to conduct the approach to that airport, as the missed approach would probably require a similar climb gradient to that of the SID, especially at airports with large obstacles.

Has anyone ever seen a min. climb gradient posted on an approach for its missed approach?

Thanks

SW

Panama Jack · Post by **Panama Jack** » Thu Mar 25, 2004 11:31 am

Approach Climb:

This segment begins when the gear is retracted, flaps are in the appraoch position, one engine windmilling and the remaining engine(s) at go around thrust.

Airspeed= Vref + 10
Flaps= Approach Config
Climb Gradient= 2.1%

Balked Landing Climb:

This segment begins when an all engine go around is initiated at 50' AGL and the engines have reached go around thrust.

Airspeed= Vref
Flaps= Landing Config
Climb Gradient= 3.2%

SpeedWeasel · Post by **SpeedWeasel** » Thu Mar 25, 2004 12:07 pm

Thanks Panama Jack,

Do you know if that 2.1% climb gradient for the approach climb is just an aircraft certification requirement or are all missed approaches based on 2.1% or less to provide obstacle clearence? As 2.1% seems a litlle shallow to avoid those mountains out in Colorado or BC.

Thanks again,

SW

Panama Jack · Post by **Panama Jack** » Thu Mar 25, 2004 12:47 pm

§ 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 for such a certificate or change must show compliance with the applicable requirements in this part.

So these are aircraft certification requirements. You are correct, they may not always meet terrain clearance requirements. In such areas, special "escape" routings are published (either higher rates of climb for successful go arounds, or complex routes). I have seen one approach plate for an airport in Alaska that warned "successful missed approach improbable" due to the rapidly rising terrain at the one-way airport.

If you want to sift through the legalese, you can do so (look for § 25.119 and § 25.121) here:

http://ecfr.gpoaccess.gov/cgi/t/text/te ... ain_02.tpl[/url]

oldtimer · Post by **oldtimer** » Thu Mar 25, 2004 9:20 pm

Go to TC's web site and under CARS section 5 look under 523, certification standard for Aerobatic, Utility, Normal and Commuter category airplanes. 525 for transport category. This reflects the US Part 23 and Part 25. Part 23/Cars523 for airplanes with a max take-off weight of 12500lbs or less, US Part 23/ CARS 523 Commuter category foe airplane up to 19000 lbs and 19 paying passengers or less. US Part 25, CARS 525 for Transport Category, above 12,500 and more than 19 seats oor MTOW greater than 19000 lbs. US part 23 sFAR 41 category was the prototype certification category for Commuter. In Canada, we have to operate those airplanes to ICAO annex 8 which is the same as Commuter category. sFAR 41 airplanes are like the Lear 31, Beech 1900C, Metro 3, Beech 300 King Air. Commuter Category is the Beech 1900D, Metro23, Beech 350. The more engines, the higher the climb gradient. Various aircraft require different climb gradients. Basically, if it is a 523 twin engine airplane (Normal Category) with a max take-off weight of 6000lbs or less and/or a stall speed less than 61kts, (the small twin, Seneca, Dutchess, Semenole,) it does not have to have any climb performance on one. (Measured at 5000 ft at ISA 5C configured for single-engine climb) Above those numbers, climb gradient is a function of Vso. The higher the stall speed, the greater the climb. Turbine twins have to maintain a climb gradient at ISA+25. Commuter category have to maintain certified one engine inoperative climb performance. It is called Net Take-off Flight Path. Really gets complicated. Basically, one engine inoperative take-off performance to 1500 ft above aerodrome elevation. Approach climb performance is where the airplane is not commited to land which is single engine go-around. Landing climb which is two engine when the airplane is configured for landing. For take-off, !st segment is to gear retraction, 2nd segment is to 400ft, 3rd segment is flap retraction and acceleration to Vyse, Final segment is to 1500 ft. Ist has to be positive, 2nd has to be 2.4% degraded 0.8% for pilot technique etc. 3rd has to be level, final has to be 1,2%. Approach climb has to be 3.3%. Incidently, 200ft/nm climb gradient for an IFR runway equates to 3.3% climb gradient. Single engine airplanes have to have a stall speed in landing configuration of 61 kts or less. Hence, if a twin can meet that requirement, it is considered as a single as far as stay up performance is concerned. So it is perfectly legal to crash into the trees at the end of the runway once you are airborne. Read the certification standards in the CARS and if you can figure then out, PM me so I can learn them also It is pretty complicated.

Stearman · Post by **Stearman** » Mon Mar 29, 2004 7:36 am

"Ist has to be positive, 2nd has to be 2.4% degraded 0.8% for pilot technique etc. 3rd has to be level, final has to be 1,2%. Approach climb has to be 3.3%. Incidently, 200ft/nm climb gradient for an IFR runway equates to 3.3% climb gradient."

Question about 2nd segment? Can you clarify the .8% for pilot technique.

3rd segment level - for how long? is it until you have accelerated and cleaned up the aircraft?

Final segement - is this considered 1.2% till reaching atleast your MEA, or a safe IFR altitude like MSA, 100 Safe?

And one more question is their an easy way to calculate climb gradient?

Stearman Driver

oldtimer · Post by **oldtimer** » Mon Mar 29, 2004 5:30 pm

Stearman 1st segment climb has to be positive. That means as you accelerate throught V1, decision speed, and make the commitment to fly, the airpalne has to remain airborne while you retract the landing gear. In other words, stay in ground effect which lasts to 35ft. 2nd degraded means test pilots in a new airplane with perfect technique have demonstrated that 2.4% is possible but for planning purposes, degrade the average pilots performance by 0.8%. 3rd is level to accelerate from V2 to Vyse and retract the flaps. Final is to 1500 ft where it becomes an enroute climb. Remember, we are attempting to establish how much horizontal distance is required to achieve these altitudes. What is normal for a transport category airplane and now FAR23 Commuter category airplanes to determine from the performance charts V1, V2 Vyse. V1 is a decision speed. Books have been written about this subject, but basically, prior to V1, stop. After V1 continue, because you have enough performance to do so. V2 is takeoff safety speed and has to be 1.2Vs. Stay at that speed to clear close in obstructions.(400ft or TOCA Take-off clearance altitude.) Accelerate to best single engine climb speed to 1500 ft. Now go to the airport runway analysis and determine what is the maximum weight that you can take-off at and meet that performance. This will allow such things as a take-off in 1/4 mile visibility because a high speed reject is a violent and dangerous maneouver so after V1, come hell or high water, you are going. Mind you, the airplane has been designed to go. Some airplanes even have methods of increasing horsepower with water/ alcohol injection to make the climb gradients. Also the engines and nacelles are designed to withstand a fire of 1100c for 5 minutes without disaster. Electrical components required for safety have to withstand the fire for 15 minutes and still preform their function. So a take-off, at least for decision making is a bit easier. Before V1, we stop, after, we go. if weather precludes an immediate return, we have to have an airport with weather within 60 min cruise on one engine. Approach climb is where we have done an ILS to minimums and in the go-around, one engine fails. We have not configured the airplane for landing. Many airplanes, the approach is flow with approach flap and landing flap selected when visual below cloud. Balked landing is where we have commited to a landing and are forced into a go-around. Full flaps, power decreasing, speed decreasing, a low energy state. go-around is 2 engine. Hope this answers your question

Flying Nutcracker · Post by **Flying Nutcracker** » Mon Mar 29, 2004 6:54 pm

Wouldn't the 0.8% allow some room for retracting gear. V2 should be attained at 35 feet AGL and at that very same point you (from my understanding) retract the gear and then you enter the 2nd segment ? Am I right??? Pilot technique can also be seen as attaining V2 at different AGLs thereby changing the gradient by retracting the gear at different times.

Cool topic! It's been a while since I've cracked some nuts!

FN

oldtimer · Post by **oldtimer** » Mon Mar 29, 2004 7:16 pm

My comments wer not so much a subject for discussion about pilot technique but more about the mimimum performance that the airplane has to demonstrate it is capable of achieving during certification flight testing in order to recieve the coveted certified one engine inoperative take-off performance. And yes, if you can achieve better performance, by all means go ahead, but in my position, as ground school instructor, I have to teach what is the required performance to meet the standard. One thing that is different between Part 23 Normal Category airplanes and PART 23 sFAR 41 and PART 23 Commuter Category airplanes is that the newer and larger airplanes require that the technique used by the test pilots to achieve charted performance has to be published in the AFM and has to be repeatable by pilots of average experience and skills. That is why you can go down to the Piper store and cross their palms with much gold and they will give you the keys and you can just jump in and go. A dumb thing to do but legal. Go to the Beech store and buy a B 350 and they have to teach you how to fly it. It is called a type rating. Guess what they teach you????

Stearman · Post by **Stearman** » Tue Mar 30, 2004 7:25 am

So the airplane is certfied for 2.4% for second segment, but for planning because I am not as good as a test pilot. I should figure on 2.4 -.8 = 1.6% with one engine. Well if this is true then and SIDs are normally 3.3% unless it is otherwise stated, would this mean that legally you can't accept a SID departure unless you can mantain 3.3% on one engine? And will have to opt for a Visual departure or some kind of alternate plan.

Stearman

SpeedWeasel · Post by **SpeedWeasel** » Tue Mar 30, 2004 1:13 pm

Stearman, I beleive that in a transport catagory aircraft you must be able to maintain the climb gradient on a SID with an engine out to accept it, whether that is the standard 3.3% or a higer posted gradient.

If you cannot meet this gradient you must depart visually or see if ATC can modify your departure.

Apparently the FAA has an office at the tower in Eagle, Colorado and they hand out fines to those accepting the SID.

oldtimer · Post by **oldtimer** » Tue Mar 30, 2004 3:25 pm

Stearman - you are correct, except to remember that the clmb gradient is the absolute minimum that will be acceptable to earn certification on a particular type. Most will do much better. Rough rule of thumb. @ 120 kts ground speed you will need to maintain a vertical speed 0f 660 ft/min to maintain a 3.3% gradient. That is 200 ft/nm. If the departure procedure requires higher gradient, then reduce the gross weight till the numbers match or wait to the cool of the evening or increase the horsepower of the engine. In a Metro 3, dry power, power not augmented with water/methanol is 1000 hp per engine with a decrease as temps go above ISA standard but wet, with augmentation, power is restored to 1000 hp plus we can add another 100 for 1100 hp. The Gulfstream was 1910 dry and 1990 wet. Using w/m will increase our max take-off weight by almost 1500 lbs. More on a hot day. What we are attempting to do is calculate whether or not we can climb straight ahead and clear all obstructions because the landing speed is so high that an off-airport landing will probibally not be survivable. What has happend since 1990 is the new certification standard which says we can operate small airplanes (US FAR 23) over 12,500lbs but we must maintain stay up capabilites if one quits. And yes, it is a limitation.

J31 · Post by **J31** » Wed Mar 31, 2004 1:10 pm

Well Oldtimer that is the best layman description of Net Take-off Flight Path that I have ever heard! You should educate some TC types in senor management positions that have very little knowledge on this subject.

I know there are a lot of Commuter aircraft the likes of Jetstreams, Metro’s, Beech 1900’s that are flogging around out of strips without consulting a chart to see if they meet the CAR’s performance criteria. The problem is a lot of 704 operators do not understand the legal requirements and it cost some serious money for airport runway analysis charts.

To be fair it is a very complex subject and Commuter operations need to get airport runway analysis charts from people like Jeppson. Trying to use the flight manual charts is very time intensive and plotting obstacle clearance above 1500 feet is all but impossible without specific airport obstacle data. One thing to get to 1500 feet on the prairies but quite another to get out of a hole like Castlegar on one engine.

Stearman · Post by **Stearman** » Sun Apr 04, 2004 8:33 am

Old Timer,

I am still not getting it here. I have a good handle on everything you are saying and about the climb gradient being the absolute minimum for certification. But this .8% thing has me confused is this number just a nice to know #? Or is it as I suspect the margin at which you could expect obstacle clearance by .8% gradient of the 2.4% that you use for flight planning purposes.

J31,

I agree with you its a pretty good discription, but the aircraft you are mentioning are commuter catergory? Now we are talking about transport catergory certification are we not?

I would think there are some slight differences for commuter. I would think that really we would be talking of just some different gradient # maybe. Its probably worth discussion, eh.

Stearman

oldtimer · Post by **oldtimer** » Sun Apr 04, 2004 1:07 pm

For Stearman and J31.
This is a fairly complicated subject that I find very few pilots understand completley and yet it is important. I have to leave now to take my granddaughter for a walk so I will put something to gether and post it at a later date. Maybe this evening.

oldtimer · Post by **oldtimer** » Sun Apr 04, 2004 7:26 pm

Well I'm back from my afternoon constitutional and the computer is free. so here I go with another longwinded story.
Basically, all pilots have to live within the limitations of their airplane and depending on the complexity, the more the limitations. Look at the performance charts for a Navajo. Take-off to 50 ft charts, Accelerate, Stop charts and then single engine climb and twin engine climb. No single engine take-off charts because the airplane does not require it due to certification standards. US PART 23, CARS 523 requirements for small airplanes, those with a MTOW of 12,500 or less have climb performance calibrated at 5000 ft, ISA (+5C) configured for single-engine cruise. Basically, if the airplane has a MTOW of 6000 lbs or less and a Vso of 61 kts or less, climb performance has to be calibrated. Climb performance can be negative or positive. Will the Apache climb on one, maybe but maybe not. Over 6000/61kts it is a function of Vso. (Minimum climb gradient of 1.5% CARS 523.67) It must climb. Hence all Navajo's and Cessna 402 etc are turbocharged to meet the performance requirements.
Turbine airplanes with less than 9 excluding crew have to do it at a higher altitude. Turbines with up to 19 passengers have Accelerate stop charts and accelerate go charts which are not quite the same. FAR 23/CARS 23 Commuter Catergory have to meet one engine inoperative take-off performance which is the same as FAR 25/CARS 525 Transport category airplanes. You have limitations and you have to live with them. Do what you have to do but live with then. For a King Air 350, we have 1100 hp per side in a 15,000 lb airplane so that is not too difficult. Limitations are. 1. Max structural weight 2.Tire speed. 3. Brake energy. 4. take-off to 50 ft. 5. Accelerate to V1 and stop. 6. Tak-off to 50 ft'. 7. Single engine take-off to 35'. 8. single engine first segment climb. 9. second segment climb. 10. fial segment climb to 1500 ft. 11. Enroute climb. 12. Minimum single engine service ceiling. 13. absolute service ceiling. 14. Approach climb. 15. Balked landing climb. 16. Landing distance ( for 704 operators, land within 70% of the runway) 18. Landing brake energy. 19 Landing tire speed. Just go to the charts and find what is most restrictive.
Hope this helps. Any more questions and I will be glad to answer them. That is what I do for a living now.

J31 · Post by **J31** » Mon Apr 05, 2004 3:43 am

Stearman wrote:
J31,

I agree with you its a pretty good discription, but the aircraft you are mentioning are commuter catergory? Now we are talking about transport catergory certification are we not?

I would think there are some slight differences for commuter. I would think that really we would be talking of just some different gradient # maybe. Its probably worth discussion, eh.

Stearman

The thread with started with “commercially operated, twin engine, turbo-jet aircraft” but the engine out climb requirements are the same for transport and commuter category in Canada and the US. I’m glad that oldtimer is touching on Air Taxi and Commuter aircraft performance because this discussion also applies to smaller aircraft. Few pilots have much of an understanding on this subject and this is a great discussion.

I think it is very important for the pilot or operator going from a Air Taxi CAR’s 703 King Air to a Commuter CAR’s 704 Jetstream understand that you now have single engine climb gradients on one engine not just two!

Many pilots and operators of CAR’s 704 Commuter category aircraft in Canada view this subject with blank stares mainly because they do not understand the regulatory requirements.

Yes you can get into the flight manual and work out the weight that will give you the % climb required for the segment of flight but that is very time consuming and daunting task

. Tabulated charts like Jeppson or Aero Data or ? make the math much simpler but they are airport specific.

Stearman · Post by **Stearman** » Mon Apr 05, 2004 9:27 am

The following is part (c) of 523.67 as related to Commuter catergory aeroplanes. I left everything prior to part (c) out due to it relating to other then commuter. This way we could look at the comparisons between commuter and transport catergories. CARs 523 (commuter)is also in blue and CARs 525 (Transport) is in green.

If you want just skip to the bottom and you will find the differences I have found between the two.

523.67 Climb: One-Engine Inoperative

(c) [ For commuter category aeroplanes, the following apply:

(1) [ Takeoff; landing gear extended. The steady gradient of climb at the altitude of the takeoff surface must be measurably positive for two-engine aeroplanes, not less than 0.3 percent for three-engine aeroplanes, or 0.5 percent for four-engine aeroplanes with:

[(i) The critical engine inoperative and its propeller in the position it rapidly and automatically assumes;

[(ii) The remaining engine(s) at takeoff power;

[(iii) The landing gear extended, and all landing gear doors open;

[(iv) The wing flaps in the takeoff position(s);

[(v) The wings level; and

[(vi) A climb speed equal to V2.

(2) [ Takeoff; landing gear retracted. The steady gradient of climb at an altitude of 400 feet above the takeoff surface must be not less than 2.0 percent for two-engine aeroplanes, 2.3 percent for three-engine aeroplanes, and 2.6 percent for four-engine aeroplanes with:

(i) [ The critical engine inoperative and its propeller in the position it rapidly and automatically assumes;

(ii) [ The remaining engine(s) at takeoff power;

[(iii) The landing gear retracted;

[(iv) The wing flaps in the takeoff position(s);

[(v) A climb speed equal to V2.

(3) [ Enroute. The steady gradient of climb at an altitude of 1,500 feet above the take-off or landing surface, as appropriate, must be not less than 1.2 percent for two-engine aeroplanes, 1.5 percent for three-engine aeroplanes, and 1.7 percent for four-engine aeroplanes with:

[(i) The critical engine inoperative and its propeller in the minimum drag position;

[(ii) The remaining engine(s) at not more than maximum continuous power;

[(iii) The landing gear retracted;

[(iv) The wing flaps retracted; and

[(v) A climb speed not less than 1.2 VS1.

[(4) Discontinued approach. The steady gradient of climb at an altitude of 400 feet above the landing surface must be not less than 2.1 percent for two-engine aeroplanes, 2.4 percent for three-engine aeroplanes, and 2.7 percent for four-engine aeroplanes, with:

[(i) The critical engine inoperative and its propeller in the minimum drag position;

[(ii) The remaining engine(s) at takeoff power;

[(iii) Landing gear retracted;

[(iv) Wing flaps in the approach position(s) in which VS1 for these position(s) does not exceed 110 percent of the VS1 for the related all-engines-operated landing position(s); and

[(v) A climb speed established in connection with normal landing procedures but not exceeding 1.5 VS1.][/color]

The following is transport catergory 525;

525.121 Climb:

One-Engine-Inoperative

(a) Take-off; landing gear extended. In the critical take-off configuration existing along the flight path (between the points at which the aeroplane reaches VLOF and at which the landing gear is fully retracted) and in the configuration used in 525.111 but without ground effect, the steady gradient of climb must be positive for two-engine aeroplanes, and not less than 0.3 percent for three-engine aeroplanes or 0.5 percent for four-engine aeroplanes, at VLOF and with:

(1) The critical engine inoperative and the remaining engines at the power or thrust available when retraction of the landing gear is begun in accordance with 525.111 unless there is a more critical power operating condition existing later along the flight path but before the point at which the landing gear is fully retracted; and

(2) The weight equal to the weight existing when retraction of the landing gear is begun, determined under 525.111.

(b) Take-off; landing gear retracted. In the take-off configuration existing at the point of the flight path at which the landing gear is fully retracted, and in the configuration used in 525.111 but without ground effect, the steady gradient of climb may not be less than 2.4 percent for two-engine aeroplanes, 2.7 percent for three-engine aeroplanes, and 3.0 percent for four-engine aeroplanes, at V2 and with:

(1) The critical engine inoperative, the remaining engines at the take-off power or thrust available at the time the landing gear is fully retracted, determined under 525.111, unless there is a more critical power operating condition existing later along the flight path but before the point where the aeroplane reaches a height of 400 feet above the take-off surface; and

(2) The weight equal to the weight existing when the aeroplane’s landing gear is fully retracted, determined under 525.111.

(c) Final take-off. In the en route configuration at the end of the take-off path determined in accordance with 525.111, the steady gradient of climb may not be less than 1.2 percent for two-engine aeroplanes, 1.5 percent for three-engine aeroplanes, and 1.7 percent for four-engine aeroplanes, at not less than 1.25 VS and with:

(1) The critical engine inoperative and the remaining engines at the available maximum continuous power or thrust; and

(2) The weight equal to the weight existing at the end of the take-off path, determined under 525.111.

(d) Approach. In the approach configuration corresponding to the normal all-engines-operating procedure in which VS for this configuration does not exceed 110 percent of the VS for the related landing configuration, the steady gradient of climb may not be less than 2.1 percent for two-engine aeroplanes, 2.4 percent for three-engine aeroplanes, and 2.7 percent for four-engine aeroplanes, with:

(1) The critical engine inoperative, the remaining engines at the go-around power or thrust setting;

(2) The maximum landing weight; and

(3) A climb speed established in connection with normal landing procedures but not exceeding 1.5 VS.

1st segment climb appears to be the same for both catergories.

2nd segment climb for transport catergory is 35' to 400' is of course 2.4% - 2 engines, 2.7% - 3 engines, 3.0% for 4 engine aircraft.

Yet for commuter catergory it is 2.0% - 2 engines, 2.3%- 3 engines, 2.6% -for 4 engine aircraft. And it also states at an altitude of 400' above the airport surface. That statement as vague as it is I think is one of the key differences along with the gradients. hmmm

The final segement climb to the enroute 400- 1500' for transport catergory is 1.2% -2 engine, 1.5% -3 engine, 1.7 for 4 engine aircraft. Transport and commuter catergories climb gradients are the same, yet again it states - at an altitude of 1500' above the takeoff surface.

It looks like that when it comes to commuter catergory and transport catergory for climb gradients after discontinued approach the gradient are the same 2.1% for 2 engine aircraft, 2.4% for 3 engine, 2.7 for 4 engines. Except for commuter aircraft it isn't measured till at 400' above the landing surface.

No wonder people are confused on climb gradient requirements when it comes to commuter catergory aircraft with wording like that. What the hell were they thinking?

Their seem to be a difference between the certification process for commuter and transport catergory.

Stearman