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Bank Angle Limits for 121

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Bank Angle Limits for 121

Old 01-31-2013, 08:04 AM
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Default Bank Angle Limits for 121

In a hypothetical discussion with asst chief pilot about certain maneuvers in the plane. One of the responses I got was along the lines of - we could never do that anyway as we're limited to 30* of bank as a transport category aircraft.

Being a newly transitioned ex-military guy, I'm not as fluent with the various FARs and stuff yet as I'd like to be (although I'm studying and trying). So, I went and searched all our manuals (AOM, GOM, Ops Specs, AFM, & SOP) and couldn't find the 30* limit anywhere other than our SOP. So I searched the FARs and could only find mention of bank angle in standards for performance after takeoff and some references in the AIM for holding procedures. Steep turns were mentioned (to 45*) for initial/recurrent training. Otherwise, very little reference.

When queried about it, he said our plane being older, was certified to CAR 4B and I did find reference to that in our AFM (also 9A). When googling that, I kept getting pointed to Part 25 for aircraft certification - which seems to discuss loading and performance capability primarily, and not operations. He implied the restriction was imposed by the FARs and our SOP was merely echoing that.

So, now that I've bored you with my google-fu (or lack thereof), my question is - Is there an FAA bank angle limit for 121 operators using transport category aircraft? If it matters, we are a supplemental 121 outfit. If so, can someone point me in the right direction?

TIA

Last edited by LowSlowT2; 01-31-2013 at 08:26 AM.
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Old 01-31-2013, 08:16 AM
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It's whatever is more restrictive the FARs or SOP. If the SOP says 30 then it's 30. However, in an emergency situation you can take whatever action appropriate, if banking more than 30 is what you need then do it.
30degrees of bank is a pretty common limitation in 121 SOP.
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Old 01-31-2013, 08:25 AM
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Originally Posted by Slats View Post
It's whatever is more restrictive the FARs or SOP. If the SOP says 30 then it's 30. However, in an emergency situation you can take whatever action appropriate, if banking more than 30 is what you need then do it.
30degrees of bank is a pretty common limitation in 121 SOP.
I understand perfectly that the rules are whatever is more restrictive. My question primarily was focused on whether or not there are bank angle restrictions in the FARs anywhere - I couldn't find them outside of very specific situations (performance after takeoff and holding).

Do they exist somewhere?

Thanks!
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Old 01-31-2013, 08:34 AM
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There may be design requirements (vice limitations) in part 25 which specify that a transport aircraft must be able to bank to so many degrees bit I don't think there's any operational limits.

Applicable company limits would be found in the SOP, and might be type-specific, although 30* sounds typical. Anything more than that would bother the pax.

There's nothing inherently bad or limiting about bank angle...it's all about the resultant G-forces so the airframe limitations are the load factors. How far can you bank in a coordinated turn without exceeding load factor limitations? 60* bank is easily within the the 2.5 LF limit which is the minimum for part 25.
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Old 01-31-2013, 08:45 AM
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Originally Posted by rickair7777 View Post
There may be design requirements (vice limitations) in part 25 which specify that a transport aircraft must be able to bank to so many degrees bit I don't think there's any operational limits.
I think the only design limits (I could find) were interpetive of the g-limit you mention below. 2.5G is about 67* or so. My AFM mentions 60* somewhere - I forget the context. So, I believe, that is limiting for our aircraft.

Originally Posted by rickair7777 View Post
Applicable company limits would be found in the SOP, and might be type-specific, although 30* sounds typical. Anything more than that would bother the pax.
Generally, we do not carry pax. However, this hypothetical discussion wound around the idea we couldn't do something because it was limited externally to our SOP and our SOP was merely restating it...

Originally Posted by rickair7777 View Post
There's nothing inherently bad or limiting about bank angle...it's all about the resultant G-forces so the airframe limitations are the load factors. How far can you bank in a coordinated turn without exceeding load factor limitations? 60* bank is easily within the the 2.5 LF limit which is the minimum for part 25.
Agreed....and was the thrust of my side of the discussion.

Of note, my 'debate adversary' does not have a military background, so all of his 'transport category' experience has been in 135 or 121, I believe. As the entirety of his experience, I am beginning to believe it is the cornerstone of his defense (ie - he's never been anywhere where >30* was permitted and assumed it was a 'universal' restriction, so must be in the FARs). As he's the asst chief pilot (and soon to be CP), I'm not quite in a position to tell him to prove it to me as I would with a peer. And, in all honesty, I'm quite happy to do the sleuthing as I learn more about the FARs by wading through them...even if it's painful.

Any ideas where I could continue my search?
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Old 01-31-2013, 09:11 AM
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Without getting into proprietary data, you would want to consult the current Advisory Circulars for how and why certain things are certified the way they are. ACs actually supercede the FARs in many cases, because they are more detailed, restrictive, and complete. I used to write cert test plans for Part 91/123 bizjets and often had to consult Part 121 ACs. The latter serve as a starting point for manufacturer- specific cert planning. You can search them for free on the FAA website, see here.
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Old 01-31-2013, 03:38 PM
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After about 30 minutes of perusal (admittedly, not exhaustive), the majority of ACs affecting transport category aircraft seem to pertain to certification. A search for "bank angle" was unproductive, but I did find the term buried in the text of at least one AC, so using the online search feature seems to have a limitation of some sort...title only, perhaps?

ACs regarding 121 operations were even less fruitful.

Did you have something specific in mind, or just the helpful prod that I took it as?

TIA
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Old 01-31-2013, 03:52 PM
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I did not have anything specific in mind pertaining to bank angle limits and as is commonly the case, Rick's thoughts are what I would have on the subject. But AC 25-7C is the gospel on transport certification, so download that whopper and search it. I do not think you can search it without downloading it your computer first. It's almost certainly a load-factor driven limit, but it's a bit more complicated when other factors such as gust envelopes, nav reception, and other things enter the picture.

Last edited by Cubdriver; 02-01-2013 at 08:07 AM. Reason: correct typo
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Old 01-31-2013, 04:05 PM
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Default Let It Be Written....

I don't think there is anything written in the FARs either, just in OPSPECs.

In the USAF, just about everyone says we are limited to 30 degrees. But when I challenge them to show me where it says that, there is no answer.

My best guess is that 30 degrees is the Air Force equivalent of SOP at an airline.

In the Air Force, the definition of 'aerobatics' is greater than 89 degrees of bank or pitch. If so doing, one must be in special-use airspace, and have a parachute.

The FARs contain a similar definition, which (I think) is 60 degrees of bank, +20, and -10 pitch. I think this is in Part 91.

Unless 121 contains a more restrictive definition, I think this would be it. The reality of most airliners being in the +2.5/-1.0 and +2.0/-0.0 range (clean and dirty, respectively) means bank would have to be limited for level-flight maneuvers.

I just can't recall ever seeing anything in writing that specified a maximum bank for Part 121.
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Old 01-31-2013, 04:10 PM
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Thanks again. Just did several variations of search in that beast. Interesting document - makes me want to be a test pilot (not really).

Again, as the overwhelming majority of the stuff I've come up with on my own, it appears this is design certification stuff. And while I guess it's conceivable you could design something with a maximum bank angle of some number of degrees, most of the maximum limits I can find are indeed load limits (2.5g - 67* in level flight). This does seem a more sensible approach to aircraft design.

I know it's not in the basic aircraft design (although certification is a different animal) because I flew the military version and wasn't limited to 30* by any rule or TO. However, I've already learned quickly that how the FAA certifies the plane has nothing to do with how the military operates an identical model!!
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