Sunday, February 07, 2010

True, False or Maybe

Instrument flying is chock full of rules and regulations. However it is also replete with gray areas, where a clear definitive answer is not spelled out. These areas are always good to spark a lively debate among pilots. Instructors are no different – we have our ideas too about the gray areas. So let’s look at a few things that are not clearly spelled out and are sure to provoke some debate.


Question 1:

Scenario: you are flying towards the IAF for the NDB or GPS RWY 34 at Cambridge (KCBG). You have been cleared for the full approach, your direction of flight is northwest and your altitude is 4000’ MSL.



After passing over the IAF, you must get established on the outbound leg with a heading of 170° in order to do a procedure turn. Which is the true statement?

· You must make a right-hand turn to get established on the outbound course because that is the protected side shown for the hold.

· It doesn’t make any difference whether you turn right or left because you are at MVA and not in any danger of colliding with an obstacle.

Question 2:

For the same approach, for various reasons you are at an altitude of 8,000’ and need to lose a lot of altitude in order to fly this approach. ATC tells you to hold south of the NDB IAF as published and descend in the hold until you reach 3,000’.


You do as directed and reach 3000’ as you are approaching the IAF on the inbound leg of the hold. ATC clears you for the full approach.


True or false:

· You must intercept the outbound leg in order to fly out and do a procedure turn.

· You can simply extend the outbound leg of the hold for two minutes or so and then turn inbound in the elongated holding pattern.

· Both procedures are acceptable.


Bonus question:

· What is DUMDY? (Hint – it is not shorthand for Descend Undercarriage Mixture Descend some more and Yippee there’s a runway in sight)


Question 3:

Now let’s look at another approach, this one is the GPS-28 approach into Maple Lake (KMGG). Scenario: you are approaching NAZMY from the east. ATC has cleared you for the approach.



You are pretty much lined up with the final approach course but the approach plate doesn’t specify NoPT coming from this direction and the 1-minute hold depicted at NAZMY is clearly meant to serve as a procedure turn.


True or false:

· You must do a turn around holding because NoPT is not specified

· You don’t have to do a turn around holding because you are more or less lined up with the final approach course


Question 4:

You are flying the full VOR-A approach into KMIC (see IAP below). You have completed your outbound leg on the procedure turn and are ready to do a 180° turn to a heading of 121° to intercept the inbound course.



You happen to glance at your DME and it reads 9 nm. The profile view clearly states the procedure turn must be done inside of 10 nm. Which of these statements is true?

· You must turn right because that is how the procedure turn is depicted on the approach plate.

· It makes no difference which way you turn, so make a left-hand turn to 121° in order to stay within the 10 nm range for the procedure turn.


Second bonus question:

You are flying single-pilot IFR and are trying to get the weather at your destination. But just about the time the ATIS report is giving the winds, ATC starts talking again so you turn down the volume on the ATIS frequency in order to hear the controller. After several attempts to get the weather, you still don’t have the pertinent information and are getting closer and closer to your destination.

What is your best course of action?


· You never leave the ATC frequency, so just hang in there and keep trying. Maybe you’ll get lucky.

· Ask ATC for permission to leave the frequency to get the weather at your destination


Answers:


As I said at the start, these are areas that can provoke a lot of discussion among pilots, so here is my two cents worth.


Question 1:

It makes no difference which way you turn in order to get established outbound.


Question 2:

Both procedures are acceptable.


First bonus question:

DUMDY is a procedural waypoint for an IFR GPS. An IFR GPS starts scaling down to 0.3 nm sensitivity two miles before reaching the FAF. However this approach does not have a FAF; you simply start to descend when established inbound. DUMDY serves as a virtual FAF for an IFR GPS. Two miles before reaching DUMDY the GPS starts scaling down to 0.3 nm sensitivity. And as a sidebar, if flying this as a GPS approach, you had better not start your procedure turn until you are south of DUMDY.


Question 3:

The second answer is correct. ATC is not expecting you to do a procedure turn. In the AIM, this is clarified, and controllers will often clear you straight in for the approach. If there is any doubt in your mind, however, query the controller about it.


Question 4:

The second one is preferred. It makes no difference which way you turn, and a left-hand turn will more likely keep you within the 10 nm limit.


Second bonus question:

The second course of action is preferable. You won’t read this in any book, but I have had both controllers and DPEs tell me they would prefer pilots ask for a frequency change to get the weather. Otherwise you are trying to listen to two frequencies at once and risk missing a call or not getting the weather (or both).


In the future I’ll try to delve into some of issues and questions like this. Your suggestions for future topics are welcome.





3 comments:

Anonymous said...

thank you / CCM /french pilot LFMD

Wayne Conrad said...

Linda, Welcome back! These are great questions.

On question 3, are you being vectored onto the final approach course ("N1234, turn left heading 260 vectors gps runway 28 approach") or are you being cleared for the full approach ("N1234, cleared direct nazby expect the gps runway 28 approach"). I've always thought--possibly wrongly--that it mattered: With a full approach, you'll fly the HILO even if you happen to be aligned on the FAC (unless NoPT), but with vectors to final you won't. Is this one of those times when it'd be good to ask the controller what he's expecting?

Linda said...

On question #3, by definition you are being vectored since you are not on a transition route or a published portion of the approach. The controller can clear you straight in for the approach. It would probably be something like "cross NAZMY at or above 3000'. Expect clearance for the GPS-28 approach straight in" or something like that.

This would make it clear that ATC is not expecting you to do a PT and the crossing restriction keeps you separated from the terrain since you are not on a defined route. And when you are being vectored, ATC can clear you straight in for an approach.

Hope this helps.
Linda