Min altitude during a procedure turn

[philo beddoe]

Correct-

At the boundary of the primary area, obstacle protection immediately drops to 500'.
2 nm further out it is 0'.

If I remember right, intermediate segment clearance is also 500'. I'll try to look it up.

 

[Stepclimb]

Circling Radii

This discussion brings up another TERPS discussion: In the USA, circling Radii have no buffer! Stray one foot out of your protected airspace for your category and all bets are off. Also remember that the categories are based on IAS and at high Pressure/Density Altitude airports, the prudent pilot would consider using the higher category circling MDA's since his/her TAS (and turning radius) are considerably higher.
-Regards
Stepclimb

 

[PropsForward]

Wow, what an interesting topic. I am learning quite a bit from all this.

I would like to throw a couple more items in the pot.

1. For all pratical purposes the PTS standard is +/- 100 feet except for non-precision approaches where the MDA is +100/-0.

2. Any consideration of the Plainview Symbol (MSA - Minimum Safe Altitude, etc). Most of the time they are the same or higher, but are they ever lower...

 

[JRSLim]

How much below published minimums can you fly? Minimums minus zero...and you can certainly be above them. Why would you permit yourself to go below a minimum at all?

That's what I've trying to figure out as I read this. When I was taught instruments my (bloody good) instructor told me to go below a minimum altitude was an instant checkride bust. So what if that's not what the PTS says or the regs etc. Forget about trying to figure out how far you can be below or what errors may be, set your altimeter and make your goal to be above the minimums with +50'.

As a point of interest, I flew safety pilot for a II doing aproaches into Ft. Carson here... at one point he was at MDA, centered on course and I just looked out my window and watched a smokestack go by about 300 feet below and maybe 100' to the right. Really underlined the importance of not going below minimums.

 

[A Squared]

That's what I've trying to figure out as I read this.

You folks really need to go back and read the original question. I thought I pointed this out already, but perhaps it was overlooked.

The question is how low below PT altitude constitutes a violation of the regulations. Nobody has asked about how far below *should* you go, nor has anyone *advocated* going below an altitude.

When I was taught instruments my (bloody good) instructor told me to go below a minimum altitude was an instant checkride bust.

Well he was wrong, it is not. If an examiner busts an applicant for being 30 feet below a procedure turn altitude, the examiner is in the wrong.

Forget about trying to figure out how far you can be below or what errors may be, set your altimeter and make your goal to be above the minimums with +50'..

That is excellent advice, however it fails to address the question which was asked.

It's like knowing that you have to be 6 nm off a DME arc to hit anything. Knowing that doesn't imply that I'll fly my arcs to +/- 5.5 nm, however, someday, that knowledge just might come in handy on a nasty night when things are going badly

 

[JRSLim]

You folks really need to go back and read the original question. I thought I pointed this out already, but perhaps it was overlooked.

The question is how low below PT altitude constitutes a violation of the regulations. Nobody has asked about how far below *should* you go, nor has anyone *advocated* going below an altitude.

I quoted Avbug because it was his post I was answering, since you had already answered the original question, as you pointed out. Looks to me like the discussion had expanded a little past that and I was just throwing in, just wanted to join the discussion. So with the original question answered, I still maintain - Why get into a mindframe that you can be BELOW a MINIMUM. You are correct, it is good information to know, might come in handy someday in the real world, and I'm glad I know it now - never thought about it before-- just took the minimums for minimums.

And yes my instructor was 'wrong' but she was right to get me in the mindset that minimums are minimums and going below that is not an option. Did it hurt me on the checkride to be thinking this - no, not one bit - I just made golldarn sure not to descend below mins. Why teach a student to fly thinking +-100 feet if you can teach them to fly +-50 or 20 feet.

Cheers

 

[TonyC]

Why teach a student to fly thinking +-100 feet if you can teach them to fly +-50 or 20 feet.

There is a difference between a limit and a goal. The student should know the limits, and have more demanding goals. If he thinks the goal is the limit, a small mistake can have an adverse effect.

When he's taking the checkride and happens to miss that goal, he can do one of two things. He can think he has just busted the ride by exceeding a limit, and let that failure adversely affect his performance from that point on. Or, he can realize that he missed the goal but still met the limit, and he can continue the ride without distraction. If he confuses the two, you've done him a disservice.

 

[avbug]

You folks really need to go back and read the original question. I thought I pointed this out already, but perhaps it was overlooked.

The question is how low below PT altitude constitutes a violation of the regulations.

§ 91.177 Minimum altitudes for IFR operations.

(a) Operation of aircraft at minimum altitudes. Except when necessary for takeoff or landing, no person may operate an aircraft under IFR below -

(1) The applicable minimum altitudes prescribed in Parts 95 and 97 of this chapter;

Wherein, then, is allowance made for flight below minimum IFR altitudes? Is descent below a published minimum altitude such as is indicated in a proceedure turn or the inbound course, or any stepdowns thereafter, necessary for landing? I think not. Not until reaching the VDP, MAP,or such point prior to either when descent below the published minimums is appropriate and legal for the purposes of landing, may one go. Not a foot, not a hundred feet.

Quotations of the practical test standards speak to practical tests, and are tolerances within which one may operate when taking a test for that certificate or rating. The PTS have no governing authority, nor guidance, with respect to the operating rules of Part 91, or any other subpart of Title 14, CFR.

Don't make the mistake of thinking that because one is allowed a certain margin of error on the practical test that this is applicable to real world thinking, nor should one begin to think in terms of what is allowable.

From a regulatory standpoint, one is not allowed to go below the published minimums once cleared for an approach, except for that point when one leaves minimums in accordance with 14 CFR 91.175(c). The prescribed altitudes published for a proceedure apply as minimums when cleared for that proceedure, unless ammended by ATC, and ATC can only do that when ATC has accepted responsibility for terrain and obstacle protection by providing vectors. In the absence of that, and when cleared for a published approach (other than a visual approach), one is beholden to published minimum altitudes on any given proceedure as minimum altitudes, period.

This applies regardless of the meteorogical conditions and visibility at the time the clearance to execute the approach has been granted. Further, it's been established here that not only is an excursion beneath published minimums, except in certain cases cited here, not legal regulatorily, it's most certainly an unwise act to be discouraged and not condoned.

 

[Iceman21]

I do believe the smack just got laid down.

 

[JRSLim]

There is a difference between a limit and a goal. The student should know the limits, and have more demanding goals. If he thinks the goal is the limit, a small mistake can have an adverse effect.

When he's taking the checkride and happens to miss that goal, he can do one of two things. He can think he has just busted the ride by exceeding a limit, and let that failure adversely affect his performance from that point on. Or, he can realize that he missed the goal but still met the limit, and he can continue the ride without distraction. If he confuses the two, you've done him a disservice.

And when he misses the goal and still meets the limit in the clouds, he can continue without distraction.. at least momentarily until he experiences CFIT, which I imagine is quite distracting.

 

[memooch]

Also, temp errors can be considered, but the most likely place for real peril to occur would be a medium to high PT in mountainous terrain, with very cold temperatures.
...
This is because the cold-wx error compounds with altitude above the altimeter reporting station, not your height MSL.

We also have 2,000' obstacle clearance over mountainous terrain, right?

 

[philo beddoe]

Not on prcedure segments.
Just MEA's, MOCA's, and grid MORA's.
Not even on MSA's.
Y'all be careful out there!

 

[philo beddoe]

JRSLim needs to lighten up a bit. PTS will always keep you alive in IMC.

 

[Singlecoil]

Not on prcedure segments.
Just MEA's, MOCA's, and grid MORA's.
Not even on MSA's.
Y'all be careful out there!

That is such an excellent point. I've had ground prox warnings on cold days in mountainous terrain in Oregon and Montana while being vectored. Querying the controller about their MVA's has revealed that they are 1000 agl and they make no correction on cold days, meaning they think you are 1000 agl because that is what your mode C reports, but in reality you are lower due to non-standard temperature as revealed by your radar altimeter and ground prox. Why ATC can't feed temperature into their computers like they do non-standard pressure is beyond me.

 

[philo beddoe]

Generally true obstacle protections are

1000ft normal, 2000ft mountainous:
* MEA
* MOCA
* MORA/OROCA (Jepp/NOS)
* Normal hold
* Missed approach holding point (Not sure on this one)

1000ft (generally)
* App plate MSA
* Procedure turn (primary area)
* Teardrop course reversal (primary area)
* Ractrack course reversal (primary area)

500ft (generally)
* Intermediate segment (PT inbound to FAF)
* Procedure turn (secondary area)
* Teardrop course reversal (secondary area)
* Ractrack course reversal (secondary area)

ILS
* Varies, can be as low as 120' or so

VOR/LOC/BC/GPS/DA/SDF
* 250/300ft above the controlling obstacle (FAF/no FAF)

NDB
*300/350ft above the controlling obstacle (FAF/no FAF)

Local conditions can cause these minima to be modified.

 

[philo beddoe]

Forgot one - oops!

Circling approach
* No less than 300ft above the controlling obstacle
* Never less than 350ft agl for cat A
* No less than 450 agl for cats B&C

 

[scangadah]

I was waiting for sombody to post that. Good Job Philo!
(dang, there are some smart Bastids on here) Ok i will go back and finish my
Beer(s)