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View Full Version : Glide Slope...


BEWELCH
11-04-2006, 10:42 AM
ON THE GLIDE SLOPE THERE IS A WIDE X OR SOMETHING THAT LOOKS LIKE A :confused: CROSS, IS THAT THE FAF???


Puckhead
11-04-2006, 10:47 AM
Thats a maltese cross im assuming your talking about and yes that is the FAF on a non precision i believe

aero550
11-04-2006, 11:02 AM
Thats a maltese cross im assuming your talking about and yes that is the FAF on a non precision i believe

It's the FAF on a precision or non-precision approach.


Tinpusher007
11-04-2006, 12:27 PM
On a non-precision approach, the maltese cross indicates the final approach fix. Glide slope interception on a precision approach (ILS) is considered to be the FAF and is indicated by the lightning bolt.

TonyC
11-04-2006, 12:37 PM
It's the FAF on a precision ... approach.



No.




On a precision approach (ILS) it indicates the point at which the gilde slope should be intercepted. Glide slope interception on an ILS is the FAF.



No.



A precision appraoch does not have a Final Approach Fix, per se, and the Maltese Cross has no relevance to the precision approach. It depicts the FAF for the non-precision approach.





.

BROKE CFI
11-04-2006, 01:05 PM
The final approach fix for a precision approach is glide slope interception which is indicated by the lightning bolt lookin thing. This occurs right before the maltese cross which is the FAF for a non precision approach. AIM Chapter 1

Jetalc
11-04-2006, 01:36 PM
A precision appraoch does not have a Final Approach Fix, per se, and the Maltese Cross has no relevance to the precision approach. It depicts the FAF for the non-precision approach.





.

I disagree with the first part, Tony. The FAF on a precision approach is at the published glideslope intercept altitude. It will never be higher, but it may be lower, if, for example, ATC has you holding at the OM at an altitude lower than the GS Int altitude and they clear you for the approach out of the hold...


Of course a precision approach has a FAF - otherwise how would you be able to comply with the reg that addresses visibility dropping below what is required for the approach (i.e., outside the FAF, at or beyond the FAF)?

TonyC
11-04-2006, 01:50 PM
The final approach fix for a precision approach is glide slope interception which is indicated by the lightning bolt lookin thing. This occurs right before the maltese cross which is the FAF for a non precision approach. AIM Chapter 1




The Final Approach Segment for a precision approach begins where the glideslope intercept altitude coincides with the center of the glideslope. There is no defined "point" where this occurs, no Final Approach Fix.


Glideslope Intercept altitude is depicted with a lightning bolt by some AIP providers (NOS, NOAA) and not others (Jeppesen, LIDO).




.

BEWELCH
11-04-2006, 02:03 PM
Ok, So If There Is No Maltese Cross On The Chart Where Is The Faf??

Ex:denver Intl Ils 34l Cat Ii And Iii

TonyC
11-04-2006, 02:09 PM
I disagree with the first part, Tony. The FAF on a precision approach is at the published glideslope intercept altitude. It will never be higher, but it may be lower, if, for example, ATC has you holding at the OM at an altitude lower than the GS Int altitude and they clear you for the approach out of the hold...


Of course a precision approach has a FAF - otherwise how would you be able to comply with the reg that addresses visibility dropping below what is required for the approach (i.e., outside the FAF, at or beyond the FAF)?





The second half of your post raises the very important point that we must know when we are established on the Final Approach segment. The first half demonstrates that the answer is NOT when we cross a particular point.

I just pulled up the ILS to Rwy 18R at MEM as a "random" example. (If this link doesn't work, go to Fltplan.com and navigate to MEM, and the ILS 18R http://204.108.4.16/d-tpp/0611/00253I18R.PDF )
The glideslope intercept altitude is 3000'. The FAF crossing altitude on glideslope is 1876'. Consider 3 scenarios. In each scenario, ATC clears the pilot for the ILS. When is he established on the Final Approach Segment? In scenario 1 he is vectored at 4000'. In Scenario 2, he is vectored at 3000'. In Scenario 3, he is vectored at 2000'.

In scenario 1, he maintains 4000' until intercepting the glideslope, and then begins down. On Final? No. Not until he passes the glideslope intercept altitude at 3000'.

In scenario 2, he maintains 3000' until intercepting the glideslope, and then begins down. On Final? Yes. And, it's at the same point over the ground as in scenario 1.

In scenario 3, he maintains 2000'. About 3.3 miles prior to intercepting the glideslope, he passes the same point on the ground where the airplanes in Scenarios 1 and 2 began their final appraoch segments. Is he then on the final approach segment? No. It is not until he intercepts the glideslope at HIS altitude that he is on the Final Approach Segment.


In fact, there could be an infinite number of points at which the Final Approach could be commenced on a precision approach - - but not a single Final Approach Fix. Not a Maltese Cross, not a lightning bolt, and not an arrow.





BROKE CFI - - Where in AIM Chapter 1?



.

Jetalc
11-04-2006, 03:08 PM
The second half of your post raises the very important point that we must know when we are established on the Final Approach segment. The first half demonstrates that the answer is NOT when we cross a particular point.

I just pulled up the ILS to Rwy 18R at MEM as a "random" example. (If this link doesn't work, go to Fltplan.com and navigate to MEM, and the ILS 18R http://204.108.4.16/d-tpp/0611/00253I18R.PDF )
The glideslope intercept altitude is 3000'. The FAF crossing altitude on glideslope is 1876'. Consider 3 scenarios. In each scenario, ATC clears the pilot for the ILS. When is he established on the Final Approach Segment? In scenario 1 he is vectored at 4000'. In Scenario 2, he is vectored at 3000'. In Scenario 3, he is vectored at 2000'.

In scenario 1, he maintains 4000' until intercepting the glideslope, and then begins down. On Final? No. Not until he passes the glideslope intercept altitude at 3000'.

In scenario 2, he maintains 3000' until intercepting the glideslope, and then begins down. On Final? Yes. And, it's at the same point over the ground as in scenario 1.

In scenario 3, he maintains 2000'. About 3.3 miles prior to intercepting the glideslope, he passes the same point on the ground where the airplanes in Scenarios 1 and 2 began their final appraoch segments. Is he then on the final approach segment? No. It is not until he intercepts the glideslope at HIS altitude that he is on the Final Approach Segment.


In fact, there could be an infinite number of points at which the Final Approach could be commenced on a precision approach - - but not a single Final Approach Fix. Not a Maltese Cross, not a lightning bolt, and not an arrow.





BROKE CFI - - Where in AIM Chapter 1?



.

Sorry, Tony - maybe it's me, but it seems like you're talking in circles, and saying, in a different way, what I already stated. In your first two examples, the published GS int altitude is the same, regardless of where the GS is intercepted. It is the PUBLISHED altitude that counts. You repeated what I had already said. In both cases (int at 4000 and int at 3000), the spot over the ground that is considered the FAF is the same. That is a point that can be found to have the same lat/long, GPS fix, whatever.

According to the Pilot/Controller Glossary:
"FINAL APPROACH FIX- The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol for precision approaches; or when ATC directs a lower-than-published glideslope/path intercept altitude, it is the resultant actual point of the glideslope/path intercept. I believe that's what I already said.

Not sure what you mean by "On final." You could be aligned with the runway centerline, heading toward the runway, and not even be on the Final Approach Segment (since the intermediate segment ends at the FAF, by definition). Do you mean "at the FAF?"

You state: "In fact, there could be an infinite number of points at which the Final Approach could be commenced on a precision approach - - but not a single Final Approach Fix. Not a Maltese Cross, not a lightning bolt, and not an arrow." Well, I agree with you, but that's NOT what we're talking about. We're talking about the definition of a FAF, not where you believe you're "turnin' onto final." Big difference.

A fix, according to the FAA, is simply a generic term "used to define a predetermined geographical position used for route definition. A fix may be a ground-based NAVAID, a waypoint or defined by reference to one or more radio NAVAIDs." Perhaps you have issue with the use of the FAA's word "Fix" in "Final Approach Fix," since the geographical position isn't always the same?

The FAA uses the word "Final Approach Fix" in many instances, and not unintentionally:

"(2) Glide Slope Critical Area. Vehicles and aircraft are not authorized in the area when an arriving aircraft is between the ILS final approach fix and the airport unless the aircraft has reported the airport in sight and is circling or side stepping to land on a runway other than the ILS runway. "

"The primary ILS approaches for Los Angeles are attached for reference. Both contain an abundance of “slow-down-while-going-down,” but the 25 ILS is arguably worse, because the speed brakes can be deployed on the 24 approach, and some attempt can be made to play catch up before the precision final approach fix (PFAF). "

"The final approach fix is generally situated anywhere from 3˝ to 5 miles from the runway threshold. The pilot will normally prepare the aircraft so that it is configured and ready to fly a stabilized descent by the time the aircraft intercepts the glideslope."
There isn't enough room here to post the thousands of times the FAA uses the word "ILS Final Approach Fix."

If it is the word "fix" you have a problem with, maybe you can coerce the FAA into changing it. However, stating (erroneously) that there is no FAF on a precision approach is misleading at best. Arrogant and ignorant at worst, and I'm not sure which category you fall into, since I don't know you.

BROKE CFI
11-04-2006, 03:19 PM
I'm not sure where at in AIM chapter one i dont have the book on me right now. I just know its in there cause chapter 1 is all about navigation aids (vors, localizers, glide slope, etc)

TonyC
11-04-2006, 03:42 PM
Sorry, Tony - maybe it's me, but it seems like you're talking in circles, and saying, in a different way, what I already stated. In your first two examples, the published GS int altitude is the same, regardless of where the GS is intercepted. It is the PUBLISHED altitude that counts. You repeated what I had already said. In both cases (int at 4000 and int at 3000), the spot over the ground that is considered the FAF is the same. That is a point that can be found to have the same lat/long, GPS fix, whatever.

According to the Pilot/Controller Glossary:
"FINAL APPROACH FIX- The fix from which the final approach (IFR) to an airport is executed and which identifies the beginning of the final approach segment. It is designated on Government charts by the Maltese Cross symbol for nonprecision approaches and the lightning bolt symbol for precision approaches; or when ATC directs a lower-than-published glideslope/path intercept altitude, it is the resultant actual point of the glideslope/path intercept. I believe that's what I already said.




It's not a suprise that communication is difficult when the terms used are so imprecise. We are close, I believe, to understanding the same thing. Indeed, in scenarios #1 and #2, the Final Approach Segment begins at the same geographical point, and we could measure the coordinates of that point. But that's beside the point.



A fix, according to the FAA, is simply a generic term "used to define a predetermined geographical position used for route definition. A fix may be a ground-based NAVAID, a waypoint or defined by reference to one or more radio NAVAIDs." Perhaps you have issue with the use of the FAA's word "Fix" in "Final Approach Fix," since the geographical position isn't always the same?



Now we're getting somewhere. Since the point at which the Final Approach Segment is NOT predetermined, since it is affected by the altitude at which the airplane intercepts the glideslope, there can be no point published and labeled as the Final Approach Fix. Clearly, the geographical point at which the airplane in Scenario #3 commenced the Final Approach Segment was much different than the point in #1 and #2. Which was predetermined?




Not sure what you mean by "On final." You could be aligned with the runway centerline, heading toward the runway, and not even be on the Final Approach Segment (since the intermediate segment ends at the FAF, by definition). Do you mean "at the FAF?"



By "on final" I mean established on the Final Approach Segment. For a Non-Precision Approach, that would be on course inside the FAF. For a Precision Approach, that would be on course, on glidepath, at or below the published glide-slope intercept altitude. We haven't mentioned Jepps in this discussion, yet, but for Jepps users, that means "in the feather."






You state: "In fact, there could be an infinite number of points at which the Final Approach could be commenced on a precision approach - - but not a single Final Approach Fix. Not a Maltese Cross, not a lightning bolt, and not an arrow." Well, I agree with you, but that's NOT what we're talking about. We're talking about the definition of a FAF, not where you believe you're "turnin' onto final." Big difference.



"turnin' onto final" <-- trying to put words in my mouth. I don't approach this subject cavalierly, and I don't have to believe. The transition from the Intermediate Approach Segment to the Final Approach Segment is well-defined, and it does not depend on a predetermined geographical position. I submit, therefore, that any use of the word FIX with this transition is a misnomer at best, lazy at worst.






The FAA uses the word "Final Approach Fix" in many instances, and not unintentionally:

"(2) Glide Slope Critical Area. Vehicles and aircraft are not authorized in the area when an arriving aircraft is between the ILS final approach fix and the airport unless the aircraft has reported the airport in sight and is circling or side stepping to land on a runway other than the ILS runway. "

"The primary ILS approaches for Los Angeles are attached for reference. Both contain an abundance of “slow-down-while-going-down,” but the 25 ILS is arguably worse, because the speed brakes can be deployed on the 24 approach, and some attempt can be made to play catch up before the precision final approach fix (PFAF). "

"The final approach fix is generally situated anywhere from 3˝ to 5 miles from the runway threshold. The pilot will normally prepare the aircraft so that it is configured and ready to fly a stabilized descent by the time the aircraft intercepts the glideslope."
There isn't enough room here to post the thousands of times the FAA uses the word "ILS Final Approach Fix."

If it is the word "fix" you have a problem with, maybe you can coerce the FAA into changing it. However, stating (erroneously) that there is no FAF on a precision approach is misleading at best. Arrogant and ignorant at worst, and I'm not sure which category you fall into, since I don't know you.



Like I said - - misnomer at best, lazy at worst.





.

TonyC
11-04-2006, 03:45 PM
I'm not sure where at in AIM chapter one i dont have the book on me right now. I just know its in there cause chapter 1 is all about navigation aids (vors, localizers, glide slope, etc)





Here's one right here: Aeronautical Information Manual (http://www.faa.gov/ATpubs/AIM/index.htm)




:)





.

rightseater
11-04-2006, 03:51 PM
This brings up the difference bettwen FAP and FAF. An ILS has a final approach point, not fix. It occurs at GS intercept. This may be well before the maltese cross or a little bit after it. You're not actually considered to be on the final approach segment untill you have intercepted the GS regardless of where the Maltese Cross is.

BEWELCH
11-04-2006, 04:30 PM
Why Doesn't A Cat Ii Or Iii Approach Have A Maltese Cross??

FlyerJosh
11-04-2006, 06:14 PM
Why Doesn't A Cat Ii Or Iii Approach Have A Maltese Cross??

Because by definition, a Cat II or Cat II approach is a precision approach. You won't see the maltese cross on any precision approach. It designates the Final Approach FIX for a non precision approach.

When you see the maltese cross on a regular ILS chart (Not Cat II/III) it isn't part of the "ILS" approach. It's part of the "LOC" approach, or ILS approach/glideslope out of service (IE non-precision).

sigep_nm
11-04-2006, 11:35 PM
The FAF on an ILS is for timing purposes in case of a loss of glideslope on the approach. It is used to determine arrival at the missed approach point since you will no longer be able to arrive at DH on glideslope. Not that hard to figure out.

Tinpusher007
11-05-2006, 04:56 AM
No.



No.



A precision appraoch does not have a Final Approach Fix, per se, and the Maltese Cross has no relevance to the precision approach. It depicts the FAF for the non-precision approach.





.

You are correct, I have edited my previous post.

3664shaken
11-06-2006, 01:52 PM
This brings up the difference bettwen FAP and FAF. An ILS has a final approach point, not fix.

That is incorrect the FAP = the point, applicable only to a nonprecision approach with no depicted FAF.

Pilot/Controller Glossary

3664shaken
11-06-2006, 02:09 PM
Lots of confusion on this topic.

According to TERPS

GlideSlope Intercept Altitude (GSIA) = The minimum (and maximum) altitude that you are authorized to intercept the glideslope/path on a precision approach (unless an alternate lower altitude is depicted and ATC clears you to that altitude for the glideslope intercept). The intersection of the published intercept altitude with the glideslope/path. The altitude and location of the lightning bolt symbol (end of feather on jepps) is the highest altitude at which glide slope can be used for primary guidance.

Final Approach Segment = shall begin at the point where the glideslope is intercepted, and designated FAF. At locations where it is not possible for the point of glideslope intercept to coincide with a designated FAF, the point of glideslope interception shall be located PRIOR to the FAF.

So yes we do have a FAF on an ILS it is GSIA. While this fix may not always be the same we have to have a FAF otherwise a part 135/121 pilot has no way to determine if the approach can continue if newly reported weather drops below minimums. (135.225 121.651)

Good discussion though.

Jetalc
11-06-2006, 02:38 PM
Well stated, and that is what I have ineptly been trying to say all along. Thanks for the post.

Bascuela
11-06-2006, 06:41 PM
Takeing time on the ILS: Just want to check this with you guys. We only take time on an ILS so that in the event that the GS goes inop we can convert to a LOC mins. If the the LOC MAP doesnt have DME then it must be time. Also this is assuming that we started time at the LOC FAF NOT GS intercept. Sound good?

FlyerJosh
11-06-2006, 08:33 PM
Sure, but practically speaking, if you're set for the ILS and lose the GS during the approach (inside the FAF), it's better to just go missed, set up for a non-precision approach, collect your thoughts and give it another go.

What happens if the GS goes out between the MDA and the ILS mins and how quickly will you realize it? Do you climb back up to the MDA if you're still in the soup, or just go missed? If the GS goes out, how long will it take for you to react, look at the clock, look at the plate to see the new minimums, process that mentally, double check your ground speed, reset the decision height, etc... I figure a good pilot might take 10-15 seconds, maybe more?

At 120 knots GS, in that 10-15 seconds the aircraft will travel approximately 2000-3000' and descend 50-100'. A lot can happen (in terms of approach stability) in that period, particularly for somebody that isn't 100% proficient or that's hand flying.

sigep_nm
11-06-2006, 09:51 PM
Not that hard to figure out Johs, like you said you travel pretty quick at that speed and you are talking bout 200 feet difference between and MDA and DH, go missed obvioulsy, You are bloviating over this, welcome to the no spin zone.

Bascuela
11-06-2006, 10:24 PM
Common sense left this thread awhile ago....

Anyway, if the GS goes out when under the LOC MDA then it is a required missed approach. The FARs say that any time you operate under the MDA without the 3 requirements then a missed approach is required.
:)

ERAU_IP406
11-13-2006, 04:40 PM
If you lose the GS you must go around. You aren't magically cleared for the LOC approach if the GS fails. ATC can only clear you for one approach at a time. Not only is it the rule, but it would be stupid to suddenly change from one approach to another.

Texandrvr
11-14-2006, 05:45 AM
If you lose the GS you must go around. You aren't magically cleared for the LOC approach if the GS fails. ATC can only clear you for one approach at a time. Not only is it the rule, but it would be stupid to suddenly change from one approach to another.

That is incorrect. The controller only issues you an approach clearance for the IAP title at the top of the page. Since the localizer is the non precision part of the ILS, you are cleared to fly the localizer portion any time you are "Cleared ILS". THis is true unless the controller has issued any special restrictions. Some pilots make statements like "request the localizer approach..." or "request the ILS localizer procedures". But that is technically not necessary. Either way the controller should then clear you the ILS IAP. Even if the GS is out he is supposed to clear you the ILS and advise that the GS is inop. This is all per the ATC req FAAO 7110.65 Chap 4 Sec 8.

Texandrvr
11-14-2006, 05:50 AM
The other reason for identifying the nonprec FAF while on the ILS is in order to check the glideslope crossing altitude. That's the little number between the maltese cross and the NAVAID at the top. That is the only way to ensure that you are on the correct GS. There is such a phenomenon as a "false glideslope". This check is required for AF pilots BTW.

TankerBob
01-07-2007, 10:30 PM
If you lose your glide slope and you are still above LOC mins you can still complete the approach as a LOC. Thats why you should still start your clock when you cross the FAF for the LOC, if timing is how you identify the MAP.

I dont see how you think that you are switching approaches when the LOC freq is still the same for both the LOC and the ILS.

Hope your not teaching your students to go around on the ILS 7 at KDAB.

POPA
01-08-2007, 06:49 AM
I dont see how you think that you are switching approaches when the LOC freq is still the same for both the LOC and the ILS.

It's not really switching approaches. However, if I'm on the ILS, I don't brief the step-down altitudes for the LOC approach - and I don't think I'm alone on this. Additionally, many aircraft use different configurations for precision and non-precision approaches.

TankerBob
01-08-2007, 01:48 PM
Well I do brief the step downs on the ILS, just for this very reason. I am not going to burn a couple $ in fuel to go around on an approach that I can finish. I guess if you aircraft requires a change in config, then well I guess, but I have never heard of that.

My whole thing is not having to go around unnecessarily and waste gas and ultimately your tax dollars. I think that silly.

If you go 1 dot below and you are still above LOC mins do you still go around? or you do you recapture the GS? cause if you never recapture you can still descend to the LOC mins and continue the approach. Again to facilitate not having to go around.

NE_Pilot
01-08-2007, 05:44 PM
I dont see how you think that you are switching approaches when the LOC freq is still the same for both the LOC and the ILS.

You are switching approaches, a LOC Approach is seperate from an ILS Approach. They have different minimums, different MAPs, different FAFs, one's precision and the other is not. They share the same frequency, that is true, but that does not make them the same approach.

Whether or not you should switch from one approach to the other if the GS fails, well that is up to you and the current situation you are in, and whether you are capable of switching to the other approach, or whether it would be safer to go missed and setup for another approach.

TankerBob
01-08-2007, 08:08 PM
Ok they have different mins, but they have the same Freq and the same Final Approach course. A LOC is a component of an ILS. Its not like you are switching from a GPS to a NDB or VOR. You are using the same radios and the same components and the same inbound course. Which requires very little to change except the SA to know the mins that you are using for both.

I agree if you have to change your configuration and it makes it unsafe for you to continue then by all means go around. But in a C172, you don't have to, so I wouldn't just go around. Anybody out there fly a plane that has different configurations for NON-Precision and Precision please let me know, I have never heard of that. I am not talking about config for circling approaches I am talking about non-precision and precision. Everything that I have flown so far has required final setup at the FAF, except for circleing approaches which is a different animal that I dont want to get into an discussion about now. I am curious about these planes and their configs.

AVIVIII
01-09-2007, 05:19 AM
if you are still above the MDA, why not. Just level out and see what you've got. If you see the runway, make the changes that are necessary. If not, go missed. If you can't make the changes safely, go missed. But if you are already there, might as well see if its going to be worth going around, if you are actually going to break out or not.

POPA
01-09-2007, 04:10 PM
My whole thing is not having to go around unnecessarily and waste gas and ultimately your tax dollars. I think that silly.

Not all of us are burning tax dollars. :)

POPA
01-09-2007, 04:14 PM
Anybody out there fly a plane that has different configurations for NON-Precision and Precision please let me know, I have never heard of that.

Ryan's B727 procedures have different configurations for precision/non-precision approaches; it differs in the flap settings used. I can dig up the Ops manuals next time I go home if you're really interested...

TankerBob
01-09-2007, 05:31 PM
No thats cool I was just wondering which aircraft do that. I have never been exposed to one that did. In that case then I guess going around would have to be the option.

But since my plane doesnt do that, and I dont wanna waste your tax dollars then I am gonna continue on the LOC...:D

TonyC
01-09-2007, 06:21 PM
No thats cool I was just wondering which aircraft do that. I have never been exposed to one that did. In that case then I guess going around would have to be the option.

But since my plane doesnt do that, and I dont wanna waste your tax dollars then I am gonna continue on the LOC...:D





The Air Force had a different philosophy on loss of glideslope than what I've encountered in the rest of the world. In the Air Force, the "Localizer" was just another way of flying the ILS approach. Losing the glideslope was no big deal -- it was a favorite exercise in the Simulator. We were trained, conditioned, expected to continue the approach using Localizer only procedures.

Out of the Air Force, they're treated as two completely different approaches, with different clearances, and different procedures. The philosophy is exactly opposite. Lose the glideslope, lose the approach.



Either way, the decision should never be influenced by money, tax dollars or otherwise. I hope you were being sarcastic about that.



:)





.

TankerBob
01-09-2007, 07:36 PM
Absolutely

Ewfflyer
01-09-2007, 08:59 PM
I'll probably get slammed for it, but in my opinion, if you're flying an ILS, most planes have a back-up OBS, and in that I personally always back up the #1. If I lost the GS, then yes, I would transition to the LOC mins if I have not descended below those mins. Especially since if you did a proper approach brief, you'd recognize what A:Your current Ceilings/VIS B. App mins C. Options on app D. Missed Proc So all in all, being a professional pilot, your job is to make it work, and I'll put the safety plug here, because I would never recommend something to anyone if they didn't feel safe doing it, or if it comprimised safety in the first place. Fly safe, and have fun

ToiletDuck
03-20-2007, 08:52 PM
If you are shooting an ILS.... and you lose your GS while at or above LOC mins you ARE NOT ALLOWED to continue the approach as a LOC UNLESS:


A)The approach has an approved LOC only approach(obviously)
B) ATC is notified that you lost the GS and they approve you to continue on the LOC.
C)You either started your time or you have DME setup.

Just because you are on the ILS and lost the GS doesn't give you the right to all the sudden make a dive for the MDA. IF cleared for the ILS you are only allowed to shoot the ILS until approved otherwise.

I've been reading up for my interviews and was curious about this. Used the search function to find this thread. Found several "This is what I do", "I don't know why you think that", or "You do this" statements so I started digging. What I've stated is the actual answer and may be found in (AC 61-27C).

Duck

ToiletDuck
03-20-2007, 09:03 PM
The FAF on an ILS is for timing purposes in case of a loss of glideslope on the approach. It is used to determine arrival at the missed approach point since you will no longer be able to arrive at DH on glideslope. Not that hard to figure out.

For timing purposes on an ILS so you know when you've arrived at the MAP? You don't have to go to the MAP to go missed. You follow the missed approach procedure on the plate. What if you cage a needle shortly after starting? You are REQUIRED to go miss from that point. Here is a random ILS I picked.
http://204.108.4.16/d-tpp/0703/00579I17L.PDF When you go missed on that guy just follow the instructions given. Approaches give climb instructions that clear you of obstacles before turning. If it tells you to do a turning climb then you are safe to do so as published. Where you go missed on the approach once established doesn't matter.

Texandrvr
03-21-2007, 09:42 AM
Just because you are on the ILS and lost the GS doesn't give you the right to all the sudden make a dive for the MDA. IF cleared for the ILS you are only allowed to shoot the ILS until approved otherwise.


Entirely incorrect. This has been covered more than once in other threads and I'm not going into it again. If you're not comfortable with the transition from ILS to LOC when past the FAF but above MDA, then please don't. But don't tell your "Air Force Students" that they aren't allowed to do it, because in less than six months they are going to be doing it regularly and they will realize that their IFT CFI didn't know what he was talking about.


I've been reading up for my interviews and was curious about this. Used the search function to find this thread. Found several "This is what I do", "I don't know why you think that", or "You do this" statements so I started digging. What I've stated is the actual answer and may be found in (AC 61-27C).
Duck

AC 61-27C was replaced in 2001 by FAAH 8083-15 and it says no such thing.

Your idea of turning on a MAP at any point as long as you've started your climb shows an alarming, albeit common, lack of understanding of TERPS. Rather than getting into that discussion, again search other threads where it has already been discussed, I'll simply refer you to your own reference. FAAH 8083-15 Ch 10 p. 22 says:

"If the missed approach is initiated prior to reaching the MAP,
unless otherwise cleared by ATC, continue to fly the IAP as
specified on the approach plate to the MAP at or above the
MDA or DA/DH before beginning a turn."

The handbook doesn't tell you WHY you should continue to the MAP. Most pilots probably don't care. However if you want to know why it's important please find yourself a TERPS manual, preferably something current, like change 19, and read for yourself.