DP Climb Gradient

[flydog]

Is it necessary to comply with a published climb gradient even in VFR conditions when operating under IFR either 91/135 for turbojet aircraft?

 

[avbug]

Flydog,

Where climb gradients are given, they are established to provide minimum terrain or obstacle separation. If you can maintain your own terrain or obstacle separation, you needn't comply, except when cleared for a specific departure proceedure. In such a case, the clearance is binding, along with all the applicable restrictions in the DP.

If operating under FAR 135, you are required to meet specific obstacle clearance requirements. 135.379(d) provides that within the airport boundaries you must achieve a minimum vertical separation from obstacles of 35', and a minimum horizontal separation of 200'. Once outside the airport boundaries, the minimum horizontal separation is 300'.

Your Opspecs may have specific individual limitations.

You should always consider each takeoff based on your ability to achieve the minimum climb gradient with an engine out, based on your second segment climb capability. If the issue is weather or not you can meet the minimum climb gradient with all engines running, then you need to look seriously at the takeoff and make some changes. Meeting the minimum climb gradient with all engines running shouldn't be an issue; meeting the minimum climb gradient with an engine out shouldn't be an issue, either.

If you are unable to comply with the minimum climb gradient, you should notify ATC. They are expecting the minimum, and may have specific requirements for you. You may be expected to maintain your own terrain separation, or be asked if you can maintain your own terrain separation, until a specific altitude. In congested areas, it is especially important to notify ATC if you believe you won't make the necessary gradient, as ATC may be predicating your control and separation on your ability to make the minimum. This may require special handling, and timely notice makes the job easier for everyone.

Bear in mind that the inability to meet published terrain separation criteria may be grounds for enforcement under FAR 91.13, or 91.103. There is not a specific FAR which states you must meet the climb criteria, unless it is issued as a clearance (cleared via the tambo six departure, climb and maintain...). In such a case, you must comply with the clearance, as outlined in 91.123(a). However, accepting routing which exceeds the performance capabilities of the airplane can always be grounds for enforcement, even if a clearance is not violated, or required.

Note that the criteria in TERPS, which is used to establish the published minimum climb gradient, doesn't take into account weather engines are operating or not It's simply the minimum required to clear obstacles. It is up to the operator to determine if the aircraft can do it with an engine out. Takeoff weight is limited by this ability. Operators must either show compliance with the TERPS criteria with an engine out, or show alternate routing. See FAA Order 8400.10, Volume 4, Paragraph 927(e)(2).

It's also important to note that FAR 135.379(d)(2) specifies a net flight path, which is less than the climb gradient achievable as shown in the aircraft flightmanual performance section. Net flight path is a concept that reduces the demonstrated climb gradient by a specific percentage, to ensure a safety margin. Therefore, one must be able to do more than just the minimum climb gradient to meet minimum takeoff standards.

135.379(d) does not limit the departure to climb gradient, but limits the departure by weight. This paragraph prevents an aircraft from departing at a weight greater than what would allow that aircraft to meet obstacle clearance requirements. The implication is that you need not meet the gradient, but you must clear the obstacles. If you cannot mee the gradient, you must still be able to ensure that the fligth meets the minimum obstacle clearance requirements for the departure path in use. This may, or may not, require a specific clearance (depending on the location, and the conditions).

 

[flydog]

Exactly what I was looking for. Thanks for your help

 

[profile]

Avbug is incorrect with regard to part 135 turbojet operations. There is no provision to waive climb gradient requirements under IFR, so the only way would be under a VFR on top type clearance, which is not allowed under the ops specs. Note that ATC will clear you for it regardless, as the clearance is predicated on known traffic, and they are not required to know (nor are they responsible for) the specific regulatory requirements for your operation. An ATC clearance does NOT make something legal!

U.S. Department
of Transportation

Federal Aviation Administration

MAY 25 1994

Dear Mr. Roberts:

The following information should clarify your questions regarding the IFR
requirements set forth in paragraph B33 of the standard operations specifications forFAR Part 121 and 135 operators

All FAR 121 operations and all FAR 135 turbojet operations not specifically exceptedby paragraph B33a, b, or c of the operations specifications must be conducted under instrument flight rules. No other visual flight rules (VFR) operations are allowed except those outlined in paragraph B33a, b, and c.

We understand your question regarding the request of an aircraft departing an airport with operating air traffic control (ATC) facilities for a VFR climb out to a specified altitude, this would not be an appropriate request and would be contrary to paragraph B33.

The only provisions for VFR takeoff and departure are those outlined in paragraph B33c. The provisions in B33c apply only to airports which do not have operating ATC facilities and it is not otherwise possible to obtain an IFR clearance.

Sincerely,


David R. Harrington
Manager Air Transportation Division
Flight Standards Service

 

[avbug]

I never stated that FAR 135 operators are given provision to waive climb gradient requirements. I stated that under FAR 91, operators who do not necessarily need to comply with climb gradients.

I also made it very clear that what is legal is not necessarily safe, and what is safe is not necessarily legal. The operation must be safe and legal, to be acceptable.

The applicable paragraph under FAR 135 is 135.379, which does not specifically limit departure by gradient, but by weight. This paragraph requires that the aircraft weight be limited in order to meet departure obstacle protection requirements.

The requirement to meet specific climb gradient requisites is found in OpSpec C077(d) (see copied below). This Opspec states that the crew must comply with IFR proceedures, if published for that airport, and this is a blanket requirement. It includes climb gradients.

For FAR 135 operations conducted under IFR, 91.175(f) still applies, regardless of meteorological conditions.

Under FAR 135, visual climbs are legal, but obstacle clearance requirements must still be met, based on published and available obstacle clearance data. Barring the use of the published TERPs data found in IAPs under FAR 97, then one would have to have documentation to prove adequate terrain clearance or obstacle protection, to qualify to deviate from published gradients, as given in DP's.

The applicable OpSpec items are listed below:


C077(d):
d. Terminal departures IFR. The flightcrew must comply with the departure procedures established for a particular airport by the FAA if ATC does not specify any particular departure procedure in the takeoff clearance given for that airport. The flightcrew may accept an IFR clearance containing a clearance for a VMC takeoff and climb out to a specified point in the clearance, if the limitations and provisions of subparagraph e. of these Operations Specifications are met.

C077(e):
e. Special Limitations and Provisions for Visual Flight Rules. All VFR operations authorized by this Operations Specification shall be conducted in accordance with the following limitations and provisions.

(1) The certificate holder must identify obstacles and use airport obstacle data which ensures that the performance requirements of Subpart I of Part 121, or Part 135, as applicable, are met.

(2) The weather conditions must allow the flightcrew sufficient seeing conditions to identify and avoid obstacles and safely maneuver using external visual references and to maintain minimum altitudes.

 

[profile]

Agreed except for part 135 turbojet operations, where that letter of interp officially states that VMC climbs are not authorized. I'll take Mr. Harrington's word for it, as that is the interp that the FAA Chief Counsel would accept, as would an Administrative Law Judge.

 

[avbug]

Profile,

I believe you're confusing the terms VMC and VFR. VMC refers to visual conditions, and VMC may be encountered under IFR, or VFR. In the letter you quote, Mr. Harrington specifically states that under OpSpec B33, a crew operating a turbojet aircraft under FAR 135 cannot accept a VFR climb. This is also in accordance with C077(d), which requires that the operation be conducted under IFR, and be conducted in accordance with any published departure proceedures.

However, the OpSpec also further states that the crew must comply with any departure proceedures published OR as given by ATC in the takeoff clearance.

The crew may accept a VMC climb to a given point, under IFR. This is not the same as a VFR climb, to which Mr. Harrington referred. There is a big difference between the regulation under which the flight is conducted (IFR, or VFR), and the condition of flight ("VMC" or "IMC").

 

[profile]

There is no such thing as a "VMC climb" that is different than a VFR climb. Both are terms used to describe what is really a VFR On Top type clearance. This issue was addressed in a separate letter of interp that I don't have at my fingertips at the moment, however, I worked this issue with Wally Roberts (www.terps.com) when it first came about, and am well familiar with the ins and outs of the issue!

Find me "VMC climb" in the AIM or ATC handbook. As far as ATC is concerned, you are asking for, and they are approving you for a "VFR climb" regardless of what you call it.

 

[avbug]

How about this:

"F. Clarified terminal departure IFR requirements (C077d.). It is acceptable if ATC clears the flight to execute a VMC takeoff and climb to a specified point in the clearance as part of an IFR clearance. However, the certificate holder must ensure that the obstacle performance requirements are met. Further, the flight must not depart on a VFR flight plan if the capability to go on an IFR flight plan is evident. "

You'll find it in FAA Order 8400.10, Appendix 3, HBAT notice 98-07, paragraph F(1).

Further, Paragraph E of the same bulletin specifically states the following:

"(1) It is recognized that the IFR infrastructure at certain locations may not always support an expeditious departure environment. If the certificate holder is able to show that it is just as safe to depart on a VFR flight plan at certain IFR airports, they may apply for a nonstandard OpSpec prescribing VFR departure procedures for that airport. "


In order for the certificate holder to conduct VFR operations under C077, they must have in place either a procedure or program which can identify obstacles and the airport obstacle data. Further, they must ensure use of that information by the flight crew. Although each subparagraph has specific details and minimums regarding VFR, the requirements for sufficient seeing conditions to identify and avoid obstacles is required for all VFR operations.


VFR and VMC are NOT the same thing. One may be VFR in instrument conditions, or conditions which require flight by reference to instruments, while still maintaining adequate VFR visibility and cloud clearance requirements. Night flight over water or the desert on a moonless or overcast night is such an example. One may also be IFR in visual conditions, or IFR in instrument conditions. IFR and VFR are rules, while the common useage terms "vmc" and "imc" refer to conditions of flight. Two entirely different animals.

Now, may we beat this dead horse no further?

Incidentally, a VFR-on-top clearance is an entirely different horse.

 

[profile]

If the certificate holder is able to show that it is just as safe to depart on a VFR flight plan at certain IFR airports, they may apply for a nonstandard OpSpec prescribing VFR departure procedures for that airport. "

As I said before, a point-on-point specific excemption is required. Absent that....