Isn’t ILS/LPV supposed to be “more difficult” than VOR IAP?

455 Bravo Uniform

455 Bravo Uniform

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455 Bravo Uniform
Wow, I figured doing the VOR-A at my airport would have been a slam dunk after trying a few ILS and LPV approaches. I all-sorts of screwed it up, 3 times! No issues with my lateral path, it was the step-down fixes that I kept screwing up - blowing through or deviating. I guess it’s easier to adjust power to stay on glide path/slope than to level off after each 750-950 fpm descent...I got so used to 500 fpm...think I need to practice leveling off and bringing power in about 100 ft before my target.

-Sucking in IFR-land
 
While every approach is different, there's no "need" to arbitrarily descend at 750-950 fpm on a VOR approach. Descending at your usual 500 fpm may mean you never have to actually level off at all, crossing the stepdown fix right on altitude. You just need to monitor and make adjustments.

It may or may not be "easier", but once you learn how, an ILS/LPV is certainly more straightforward, with less to worry about overall since you just follow the needles all the way down. There's all alike, that's the whole point.

And "dive and drive" at it seems you're doing is falling out of favor anyway.
 
I have a few techniques.
1. I calculate the step down rate I need to hit the next step. That is what I fly plus 100 fpm. Allows me to get to the step a few seconds before, and speed to stabilize before the next one.
2. Do the full dive model. Note throttle/MP position/power. Power to idle, nose over at 1000fpm, start pulling up 150ft before target altitude, level at altitude, as speed comes down about 5 knots above target, bring power back to previously noted setting.
3. Descend at a 3 degree down slope based on speed. For may GA planes, this is roughly 500 FPM. The plane will be slow but can usually maintain level flight with only a small power bump which is easy to take out if needed.

It sounds complicated, but I actually find the second one more intuitive for me.

Tim
 
LPV and ILS approaches at a lot easier as you are given the crosshairs-just fly it. Plus usually ATC gets you all set up so it’s a breeze. The VOR-A on the other hand is a different beast. Toss in a procedure turn and some timing and you just have a lot more going on add on the lack of crosshair like guidance- means you have more time to botch it all up.
 
Very few non-precision approaches require a 900 fpm or more descent rate to make step down fixes. Brief the approach to see if there are unusual descents required, or evaluate if a steeper than normal descent will be required due to strong tailwinds. If not, a 500-700 fpm descent will normally be ample. (I remember getting into a pickle during training on the NDB 25 at Provincetown by not flying far enough outbound on the course reversal, resulting in a spectacular rate of descent to make the MDA on time.) In my plane 100 rpm less than the power setting required for a 500 fpm descent will yield 700 fpm, and that is what I would typically aim for in a non-precision approach. That will get you down pretty quick without making it too difficult to a anticipate leveling off at the target altitude. Know your "numbers" for attitude and power for level flight and a defined fpm descent at your typical approach speed (e.g., 90 kt) so you can control your descent in a predictable way.

Brief and know your step-down altitudes, descend expeditiously (500-700 fpm), and round out well before reaching the step down altitude. If you are 100-200 feet too high for a step down it's no big deal, and you can always ease down a hair as necessary. The altitude you want to ensure getting to as closely as possible but not beyond is the MDA. If you have glass guidance, setting the altitude bug can be a reminder for step down fixes if you can manage the extra task saturation. Or you can just keep repeating the next step-down altitude to yourself until it's reached.

Flying dive and drive nonprecision approaches is not hard, but like everything else IFR, requires disciplined technique. On the plus side, you have only one CDI to center. The other axis is either level flight or a 500-700 fpm descent.

For many, many years, a lousy VOR approach was the only approach available at my home field. You figure out how to get down to minimums quick, or you miss the airport when the weather is marginal.
 
455 Bravo Uniform said:
Wow, I figured doing the VOR-A at my airport would have been a slam dunk after trying a few ILS and LPV approaches. I all-sorts of screwed it up, 3 times! No issues with my lateral path, it was the step-down fixes that I kept screwing up - blowing through or deviating. I guess it’s easier to adjust power to stay on glide path/slope than to level off after each 750-950 fpm descent...I got so used to 500 fpm...think I need to practice leveling off and bringing power in about 100 ft before my target.

-Sucking in IFR-land
Click to expand...

Different skill that needs to be practiced. I'd argue 100 feet isn't enough of a lead. The FAA requires you to maintain MDA +100/-0.
 
Good advice all, thanks.

Was trying too hard to nail +/- 0.

Then trying to get down about 800ft b/t FAF and MAP which is 3.1 mi, which should be doable.

A lot happening fast, can’t dawdle on pulling power and getting the nose down, then the opposite at MDA.

Just something new. Plus, we went missed twice, which we had never done before.
 
benyflyguy said:
LPV and ILS approaches at a lot easier as you are given the crosshairs-just fly it. Plus usually ATC gets you all set up so it’s a breeze. The VOR-A on the other hand is a different beast. Toss in a procedure turn and some timing and you just have a lot more going on add on the lack of crosshair like guidance- means you have more time to botch it all up.
Click to expand...

On my recent IPC Lance had me do a VOR/DME-A approach. DME arc to join the VOR radial, had me sweating.
 
In my experience, if you carefully brief the approach, you can determine a descent point and rate that will allow you to cross the final approach fix at the required altitude AND cross the threshold at the threshold crossing height with only minor pitch and power adjustments - a CDFA. This is the technique that FAA seems to prefer, because the power and pitch changes required by the charted profile (“dive and drive”) can cause vertigo. A CDFA is not the best technique when visibility at MDA is close to minimums, because then you want some time stabilized at MDA to scan for the lights, but if you have 3+ miles below an overcast layer, expecting to break out in plenty of time, it works “real nice, Clark”.
 
midlifeflyer said:
To answer just the title of your thread, "Isn’t ILS/LPV supposed to be “more difficult” than VOR IAP?"

No. :)
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You are hereby charged with the crime of, with malice and forethought, of answering a question with an answer to said question. How do you Plead?
 
luvflyin said:
You are hereby charged with the crime of, with malice and forethought, of answering a question with an answer to said question. How do you Plead?
Click to expand...
Guilty as charged. Especially the malice aforethought (FIFY).
 
midlifeflyer said:
To answer just the title of your thread, "Isn’t ILS/LPV supposed to be “more difficult” than VOR IAP?"

No. :)
Click to expand...
PoA family Feud, sudden Death... Top 1 answer on the board....

"Isn’t ILS/LPV supposed to be “more difficult” than VOR IAP?"

@midlifeflyer hits buzzer, answers "No"

Bingo!!!!!!!

I dont have a prize for you Mark.. but the customary good answer works... :p
 
If you want to add some difficulty to that whole, "lateral path" thingy, check out the VOR-A into KEYE.

https://flightaware.com/resources/airport/EYE/IAP/VOR-A/pdf

It seems simple when you first read it, but think about what happens at the confluence of the FAF and the "zone of confusion." Right at the FAF, your VOR starts to get squirrely, so it's easy to fall into the trap of following the needle off course rather than letting the needle just swing. Then, when the TO/FROM arrow switches, you have to get down, and maintain your course while you wait for the needle to come back. It's a bit of guesswork then as to whether you are on the right ground track or the needle just is still off due to the "cone of confusion." And, before you know it, your on top of the airport.
 
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PPC1052 said:
If you want to add some difficulty that whole, "lateral path" thingy, check out the VOR-A into KEYE.

https://flightaware.com/resources/airport/EYE/IAP/VOR-A/pdf

It seems simple when you first read it, but think about what happens at the confluence of the FAF and the "zone of confusion." Right at the FAF, your VOR starts to get squirrely, so it's easy to fall into the trap of following the needle off course rather than letting the needle just swing. Then, when the TO/FROM arrow switches, you have to get down, and maintain your course while you wait for the needle to come back. It's a bit of guesswork then as to whether you are on the right ground track or the needle just is still off due to the "cone of confusion." And, before you know it, your on top of the airport.
Click to expand...
Any time an IAP doesn't have straight-in minimums and an offset of that magnitude, you have a lousy approach, especially if weather is near minimums.
 
455 Bravo Uniform said:
can’t dawdle on pulling power and getting the nose down
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I've realized, at least in my head, that this is the point of learning the "dive and drive method." When I'm initially learning how to do step down approaches, I was way too easy and slow on the throttle to finally settle into a 600-800 fpm descent. It took 15 seconds or more. But my thought process was to set a nice 500-600 fpm descent and try to keep it relatively constant throughout the approach.

The problem is that, even in my slow Archer, taking too long to establish a "nice and easy" descent means that now you've taken too long at altitude and you need more aggressive descent. The solution, at least for me, was to understand I have to "dive" and get the nose down and pull power to maintain my airspeed without getting too fast and get the heck started going down.

This has fixed my "too slow to descend" mentality for sure, and I'll probably maintain it throughout IR training, but in real life I will probably try to spend more time setting a stable descent and not really care if I'm still 100-200 feet "too high" at each step.

In fact, my last approach was an RNAV going back into the home airport on Sunday and tower gave me a low altitude warning after getting to my next step about 30 seconds early. My instructor got on and let them know we were driving along the minimums for that step, and they were ok with that, but it also struck me that realistically speaking you don't have to be +/-0 feet at every step along the way and that may not even be smart.

For the checkride, if it's +100/-0 then I would think aiming for +50 feet is perfect since it gives you the most buffer either way.
 
midlifeflyer said:
To answer just the title of your thread, "Isn’t ILS/LPV supposed to be “more difficult” than VOR IAP?"

No. :)
Click to expand...
I have generally found an ILS to be more challenging than a VOR approach, other things being equal, because the sensitivity of the needles means that keeping them within the desired deflection limits requires flying more precisely on the former than the latter.
 
Palmpilot said:
I have generally found an ILS to be more challenging than a VOR approach, other things being equal, because the sensitivity of the needles means that keeping them within the desired deflection limits requires flying more precisely on the former than the latter.
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The reason I said "no" to "supposed to be" is that "difficult" is really in the mind of the beholder. For me, the absolute worst was an off-airport NDB approach. Until I was working on my II getting it right at any given time was sheer accident. Even once I "got it," it was because I found a way to work around my complete lack of situational awareness anytime the needle pointed anywhere other than straight ahead or behind. Yet, I see posts all the time by pilots who found it incredibly easy. I know they are not lying because my CFII was one of them.

In the more modern world, take, for example, a coupled GPS/LPV approach using a navigator and digital autopilot with full vertical navigation capability. The autopilot will fly you from the enroute structure through a "descend VIA" STAR, multiple altitudes and course changes on the approach, all the way down to DA. Some would find that super easy. Others would find setting it up too much of a challenge.
 
AU_James said:
I've realized, at least in my head, that this is the point of learning the "dive and drive method." When I'm initially learning how to do step down approaches, I was way too easy and slow on the throttle to finally settle into a 600-800 fpm descent. It took 15 seconds or more. But my thought process was to set a nice 500-600 fpm descent and try to keep it relatively constant throughout the approach.

The problem is that, even in my slow Archer, taking too long to establish a "nice and easy" descent means that now you've taken too long at altitude and you need more aggressive descent. The solution, at least for me, was to understand I have to "dive" and get the nose down and pull power to maintain my airspeed without getting too fast and get the heck started going down.

This has fixed my "too slow to descend" mentality for sure, and I'll probably maintain it throughout IR training, but in real life I will probably try to spend more time setting a stable descent and not really care if I'm still 100-200 feet "too high" at each step.

In fact, my last approach was an RNAV going back into the home airport on Sunday and tower gave me a low altitude warning after getting to my next step about 30 seconds early. My instructor got on and let them know we were driving along the minimums for that step, and they were ok with that, but it also struck me that realistically speaking you don't have to be +/-0 feet at every step along the way and that may not even be smart.

For the checkride, if it's +100/-0 then I would think aiming for +50 feet is perfect since it gives you the most buffer either way.
Click to expand...

Have you established and fly your pitch/power numbers? If you know these, you can nearly instantly "set" your desired configuration, with a few seconds delay for inertia to respond to a new configuration. If you choose a standard approach speed, no trim changes are required for most configuration changes.

For example, in my plane:
  • 2 degree nose high + 2200 rpm = level flight @90 kt
  • 1 degree nose down + 1900 rpm = 500 fpm descent @90 kt
  • 2 degree nose down + 1800 rpm = 700 fpm descent @90 kt
  • 7.5 degree nose high + full throttle = max climb @ Vy, 90 mph
If you discover/know your numbers, there is no fiddling to establish the proper climb, descent, or level flight regime. Set the rpm and attitude and you know what you will get. If you are not "flying by the numbers" you are making it twice as hard and half as effective.

Glass indicators (e.g. G5) makes it much easier to visualize small attitude changes accurately. With the old steam gauges, it was one or two dots high or low, assuming you set the indicator to zero at level flight @ cruise. But the method still works.
 
midlifeflyer said:
...For me, the absolute worst was an off-airport NDB approach....
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I can definitely relate to that, especially in a crosswind. That's why it was always amusing to me that someone felt they had to come up with a conspiracy theory to explain how the pilots flying Ron Brown to his death could screw up an NDB approach!
 
chemgeek said:
Glass indicators (e.g. G5) makes it much easier to visualize small attitude changes accurately. With the old steam gauges, it was one or two dots high or low, assuming you set the indicator to zero at level flight @ cruise.
Click to expand...
Glass indicators with enough screen space (e.g. G3x, G1000) also have a VSR indicator, which makes things even easier. Put your VSI trend bar on the VSR bug and you're good to go.
 
chemgeek said:
Have you established and fly your pitch/power numbers?
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You're absolutely right- I haven't really memorized these yet. I have a few numbers for cruise climb/descent but I've been so focused on trying to fly the approach and just stay on course that I haven't yet written down and learned my numbers for approach.

Thanks for this reminder!
 
midlifeflyer said:
In the more modern world, take, for example, a coupled GPS/LPV approach using a navigator and digital autopilot with full vertical navigation capability. The autopilot will fly you from the enroute structure through a "descend VIA" STAR, multiple altitudes and course changes on the approach, all the way down to DA. Some would find that super easy. Others would find setting it up too much of a challenge.
Click to expand...
Super easy for those trained on their high-end autopilot and have conceptual understanding. Having said that, I can only imagine how difficult it would be for a competent CFI-I to get some well-heeled SR-22 (or higher) pilot to master all of that without a really good ground trainer.
 
aterpster said:
Any time an IAP doesn't have straight-in minimums and an offset of that magnitude, you have a lousy approach, especially if weather is near minimums.
Click to expand...

This one is a LOT of fun. MSAs from the south and west make it even more fun. After cruising 10 miles away from the VOR outbound (you DID remember your 5 Ts at the VOR, didn't you? Not everyone has...) you are still at nearly 1600 AGL and less than a mile from the airport.

Screenshot_20200617-203959_Pilot.jpg
 
AU_James said:
You're absolutely right- I haven't really memorized these yet. I have a few numbers for cruise climb/descent but I've been so focused on trying to fly the approach and just stay on course that I haven't yet written down and learned my numbers for approach.

Thanks for this reminder!
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The numbers are of primary importance for instrument flight - they make the rest of the flying much easier since you don't have to think as much about speed and power, you just go to the numbers you already determined and then use your concentration for other things.

In fact, they are so important that determining them is what I will do with an instrument student on our very first flight together. Usually they will take a little refining later as the pilot gets smoother and more consistent, but right from the start you have to know your numbers.

Not sure what you're flying, but it is much easier to get and to fly the numbers in an airplane with a constant-speed prop. But it's still important in a fixed-pitch as well (just harder).
 
aterpster said:
Super easy for those trained on their high-end autopilot and have conceptual understanding. Having said that, I can only imagine how difficult it would be for a competent CFI-I to get some well-heeled SR-22 (or higher) pilot to master all of that without a really good ground trainer.
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That may well be the underpinning of the Cirrus initial and recurrent training programs they use in their centers for both owners and renters.
 
RussR said:
Not sure what you're flying, but it is much easier to get and to fly the numbers in an airplane with a constant-speed prop. But it's still important in a fixed-pitch as well (just harder).
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That's interesting. Other than the fact that pitch attitude affects RPM, I have not found it to be substantially different.
 
midlifeflyer said:
That's interesting. Other than the fact that pitch attitude affects RPM, I have not found it to be substantially different.
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It's about how a change in airspeed and change in rpm are interrelated. Say you're at cruise speed in a 172, say 2500 rpm. I'm making these numbers up since it's been a while and I don't remember. You want to fly at 90 knots, which you have already determined is 2100 rpm. So you pull the power back to 2100 rpm. But as you slow down, there is less air flowing through the prop, and the rpm sags even more, to say 2000 rpm. If you don't notice (because you already did set 2100 rpm, you think you're done with rpm), the speed keeps sagging and maybe now you're doing 80. Instead, once you get to 90 knots you have to bump the power back up to 2100 rpm to stay at 90 knots.

Compare this to a constant-speed prop where you just set it at 20" and 2300 rpm or whatever and it just takes care of itself.

Obviously many, many people have trained for their instrument ratings in fixed-pitch props. So it's not a huge factor. But the constant-speed ones take just that much less concentration that can be devoted to reading the chart or whatever.
 
RussR said:
It's about how a change in airspeed and change in rpm are interrelated. Say you're at cruise speed in a 172, say 2500 rpm. I'm making these numbers up since it's been a while and I don't remember. You want to fly at 90 knots, which you have already determined is 2100 rpm. So you pull the power back to 2100 rpm. But as you slow down, there is less air flowing through the prop, and the rpm sags even more, to say 2000 rpm. If you don't notice (because you already did set 2100 rpm, you think you're done with rpm), the speed keeps sagging and maybe now you're doing 80. Instead, once you get to 90 knots you have to bump the power back up to 2100 rpm to stay at 90 knots.

Compare this to a constant-speed prop where you just set it at 20" and 2300 rpm or whatever and it just takes care of itself.

Obviously many, many people have trained for their instrument ratings in fixed-pitch props. So it's not a huge factor. But the constant-speed ones take just that much less concentration that can be devoted to reading the chart or whatever.
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That's what I meant by pitch changing RPM in a fixed pitch prop. I guess we're just back to easy being in the eyes of the beholder. To me, having had my instrument training in a 172, setting 100-200 RPM higher rpm than target for 90 KIAS level or or 100-200 RPM lower than target when intercepting the FAF is no big deal. I've had to tweak MP almost, albeit not quite, as much

Funny. Just the other day I did some personal instrument work in a BATD simulating a simple Piper Archer, so I was doing exactly that.
 
It's been a long time, but I recall using MP. With a fixed pitch prop it was what is was. With a variable pitch prop it was set for missed approach, not for final approach airspeed.

Or, am I missing something? I am more conversant with EPR and fuel flow.
 
aterpster said:
It's been a long time, but I recall using MP. With a fixed pitch prop it was what is was. With a variable pitch prop it was set for missed approach, not for final approach airspeed.

Or, am I missing something? I am more conversant with EPR and fuel flow.
Click to expand...

There is typically no MP gauge on an airplane with a fixed-pitch prop (like a Cessna 172).
 
RussR said:
There is typically no MP gauge on an airplane with a fixed-pitch prop (like a Cessna 172).
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I didn't remember that. Most of my GA time (at least instrument training was with variable prop airplanes.) OTOH, then there were the air knockers, which I flew a lot.
 
My non-precision 800 fpm needs about 7-9 degrees nose-down and 10-11” MP to get 90 kts. We did power settings many flights ago. It was quite unnerving the first time we did that so close to the ground on the VOR-A.
 
aterpster said:
I didn't remember that. Most of my GA time (at least instrument training was with variable prop airplanes.) OTOH, then there were the air knockers, which I flew a lot.
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Yes, Fixed pitch prop airplanes have only one power lever - a throttle - and one power gauge - calibrated in engine RPM. I guess I could add "typically" but I've never seen one with a MP gauge.
 
midlifeflyer said:
Yes, Fixed pitch prop airplanes have only one power lever - a throttle - and one power gauge - calibrated in engine RPM. I guess I could add "typically" but I've never seen one with a MP gauge.
Click to expand...

I've seen a few. An early 172, I think, and maybe a Stinson. No idea if they were standard equipment, factory options, or just added at a later time.
 
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