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Timing is everything... Well not really.

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John Hewlett

Jul 14, 2002
ILS approaches are timed approaches. Timing should be done as you cross the FAF inbound on the approach. However if all is well on the approach timing shouldn’t play a big factor. An ILS approach can be completed with a dysfunctional glide slope. LOC minimums are published for the approaches in the event of glide slope failure.

I fly in and out of Cape Girardeau Regional Airport (KCGI) on occasion. There for I will use that airports ILS runway 10 approach as an example. This is my normal procedure to flying the ILS 10 approach. I fly in from the southeast almost every time. The IAF is the Dutch NDB/LOM. There is a one minute hold for this approach, standard hold over the NDB. This hold is not required. I fly a parallel entry to a hold that I am not going to do. Fly back to the NDB, which also for all practical purposes serves as the FAF. I cross the NDB, the glide slope is active. I start my time. Now it should take me 3:56 to get to the MAP which is the MM. I fly a category B aircraft thus the approach should be flown at 90 KIAS. As you probably know the components of an ILS include, localizer, Glide slope, lighting, and marker beacons. Fortunately for us as pilots all of these things make ILS approaches extremely precise. That’s the norm.

Now let’s throw a problem in there. Your glide slope just became active and your time has started. The time is now 1:00 on the clock. You are doing your scan. When your vision comes back to the glide slope it is centered and there is a GS Inactive flag there. You have no glide slope. However your time as been started. Look at your approach plate, under the profile view. You will read (on this approach) S LOC-10. Your MDA (formally your DH) is now 860 feet instead of 538. However now you have an advantage. Your time has been started and you that you have 2:56 seconds at 90 KIAS left before you should be at your MDA. With out the time started, all you could do would be to come down to MDA and take a peak. Starting your time can mean the difference between landing and going to your alternate. If you get down early on the LOC you can always fly to the 3:56 and see if you see the runway environment.

As far as the LOC goes, if there is a full scale deflection. You should declare a missed approach. Time really isn’t an issue there. Always keep in mind that as the PIC you can declare missed anytime you want if you feel something fishy going on. On one more note and this really isn’t something that makes a whole lot of difference but most Airspeed Indicators read in MPH. If you want 90 KIAS look at the inner ring on the airspeed indicator.

Hope this helps!
All of that maybe fine at 90 kt approach speed. But having something (GS) flag in the final segment of the approach and then looking back to the approach plate for the new minimums, the timing involved, etc at higher approach speeds and you are putting yourself in a corner. My experience has been that timing often is a bigger distraction than its worth. No requirement to time an ILS approach. IF i am inside the FAF on an ILS - and that means GS intercept, not necessarily the FAF that is depicted for LOC/GS inop approach - and the GS flag comes up (of course you checked NOTAMS didn't you), I'm waiting to see what esle is going to fail. If I have the luxury of going around (you do have conservative fuel reserves planned in lousy weather don't you?) I do alert ATC of my equipment failure per the regs and querry them to the GS outage. Then I can better assess the problem and select the next appropiate approach. On a LOC approach with MAP determined by timing then I will use a timer (you are pretty sure about your groundspeed and you are on a stable airspeed approach, right?). Use it on an ILS but be sure prior to starting the approach what you are going to do and at what altitude you are going to do it if the GS gives up the ghost. Is it your equipment or theirs? Don't think you have to save the day by continuing an approach that has become suspect midway through it.
Also, what makes you say that the holding pattern (in lieu of a PT) depicted on this appr. is not required. Approaching the from the SE using the entry you described is fine and if you are on the proper altitude you will not have to make any circuits, but you are still considered in a holding pattern as soon as you made the initial entry even though you may not be required to trace the whole racetrack outline. Just be careful of your wording on a checkride. As you move up in more advanced/newer aircraft, there will be no more MPH to KTS scale to figure out. They are all in KTS.

I understand your reasoning in timing an ILS approach, which would work fine if you were flying a C172 or Warrior, but I think the original question was in relation to airline flying. In your scenario timing the ILS could mean the difference between landing and having to go to your alternate in a comm failure situation. (You don't have to go to your alternate if you miss on the first approach as long as you still have radio communication.) However, airlines have SOPs that their pilots must follow and it is my understanding that many of these airlines SOP would call for a missed approach if the GS failed during the approach. Flying the approach at 90 KTS vs. 140 or faster is a little different. Things happen faster and there really isn't time to be looking at your lap to find out the new mins for a LOC approach. It is best to execute the missed approach and come back for another try after briefing the approach thouroghly. It takes a few minutes to brief an approach the way most (if not all) airlines do it. To brief both the ILS and LOC approach would be way too much infomation to remember and wouldn't do you any good.

Also one more thing. You mentioned the times that you use when you do time the approach. Make sure you are taking into account the winds. If you have a tailwind while shooting the approach, you will need to reduce the time that the approach calls for because you will have a faster ground speed and will thus get to the MAP faster. The opposite is true if you have a head wind.

Again, your way does work and I don't really have a problem with it as long as you can handle it. When things are happening twice as fast and you are in hard IFR, it is just safer to execute the missed and come around again should the GS fail during the approach. Anyway, just my .02!

Fly safe!
ohhh ok

ahhh ok,

Sorry I didn't realize it was strictly an airline question. I just thought it was a regular ILS question. My wording was a bit sketchy there. When I meant "Difference between a landing and a missed to the alternate". I was just reffering to the minimum altitude, and visibilty. I totally understand where you both are coming from. One thing goes wrong that I think is signifigant enough (with my equiptment) and if its a safe move, I may declared missed and go into a hold so I can work the problem or if I can land, runway in sight etc. I will do that instead.

I just think its a good idea for someone like my self flying light aircraft only to multi-task as much as possible in simulated instrument flight. That somewhat "pointless" multi-tasking is great practice for the real thing and should make it easier.

As far as the hard IFR goes, I can totally understand that. When it goes from simulated to actual the pace of the game changes big time! And when you are flying the nifty wings like you guys it happens much much faster.

Hope I didn't upset anyone. I have to watch what I say around all the ATP's here. I am green with envy of you guys! I can only hope that I will be on the same level in a few years. Keep up the flying fellows.

No offense taken... just a friendly conversation among pilots! I think the point that can be taken from this thread, and the original thread, is that there are some differences in flying light aircraft and the faster T-props and jets found in the corporate and airline sectors.

As far as being green with envy on the equipment we are flying... don't! The grass is always greener on the other side. I got to fly a C-210 the other day, which is quite a bit smaller than the King Airs and Caravans i've been flying lately. It was so cool to be flying a small recip again! I finally got to play around a little! The most exciting part of flying the "bigger" stuff is the takeoff and landing. Sometimes I miss flight instructing because we actually got to do some maneuvering and push the planes to their limits!

Have fun!
Agreed. Not trying to make arguements just observations.
Being an instructor (former) myself with 900 dual given, I can say there is a time and a place for making the training enviroment challenging and seeing how much (multi-tasking) a student can take. I think some training schools get carried away with their training styles. They either seam to be ultra standardized and airline oriented (or think they are) or very non-standardized. I think more common sense stuff needs to be taught (which comes with experienced instructors) than mindless dedication to a "standardized" operating procedure. (Usually with many flight schools they are anything but standard) The most important thing is to treat your everyday flying like your training and vice versa. If you are doing exercises and procedures during training that you don't do during "normal" flying and vice versa, then there is probably little value in those procedures. There is an expression "fly like you train and train like you fly." Keep it simple and safe.
Get to the MAP

"As far as the LOC goes, if there is a full scale deflection. You should declare a missed approach. Time really isn’t an issue there. Always keep in mind that as the PIC you can declare missed anytime you want if you feel something fishy going on. On one more note and this really isn’t something that makes a whole lot of difference but most Airspeed Indicators read in MPH. If you want 90 KIAS look at the inner ring on the airspeed indicator. "

john, remember that the TERPS manual and the AIM's both state that you need to be at the MAP to excecute the missed. If you are in contact with ATC (which isn't always the condition) then you can declare the missed and get instructions from them. If you are in a mountinous area, and not in contact with ATC, you need to try to get to the MAP. This is because when the approach was designed, there were certain obstical clearance criteria that have to be met. If you simply start the missed say 3 miles out, you could run into something. Additionally, in a lost commo environment, you also need to get to the MAP because ATC will expect this and they will clear the airspace accordingly. They are not expecting you to make a turn 3-5 miles out. When DME is not avail, time is all you got to get you into the vacinity of the MAP. Remember what the regs say about full scale deflection? In the case of a Loc, turn to a heading that that will help you retrack and dont descend untill you are on the Loc and know where you are in relation to the approach. In the case of GS, STOP your descent unless you know exactly how far out you are as you could actually fly over the GS antenna and hit the ground. I have seen this in the sim several times with students. If you were below the GS, start a climb! For individuals without DME, time is your only backup. I dont consider this multi tasking or overloading the student. I teach it to become automatic and it is part of the approach brief. If single pilot, I still brief myself and have a plan. ;)
I really can't believe anyone would think it is OK to start turning away from the published procedure prior to the MAP. I think some are just confusing the terminology here. "Declaring missed approach, going missed approach, and flying the missed approach" get mixed up here. Nothing wrong in declaring a missed approach prior to getting to the MAP (laterally). I'm sure the arguements will come in on the appropriate altitude to initially climb to. I put my vote in for climbing to the final MAP altitude as long as you meet any of the intermediate altitude restrictions after the MAP and fly the ground track profile. Any ATC folks out there to comment on any concerns regarding this and in particular how an early climb may interfear with other traffic?

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