I'm feeling that the typical VASI glideslope is a little low

SixPapaCharlie

SixPapaCharlie

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2 whites and 2 reds at a couple different airports and most of final I know I couldn't make the runway if my engine died.

Is it designed to be an angle at which you should be able to make the runway or is 3 degrees (I think that's it) specified for a different reason?

Anyone else feel low when tracking into these things?
 
IIRC its designed for instrument approaches. Not for best glide.

But I'm probably wrong, thought I remembered someone telling me that....
 
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They're way too low for me, but I do power off approaches. At my home 'drome, if I don't see four white when I turn final about 1/2 mile out then I'll likely need to add power to make the runway <fail>.
 
If my math is right a 3 degree glide slope is about a 20:1 glide ratio, Very few small aircraft will glide that well. For Day VFR flying in most single engine airplanes the glide slope is just an indicator to keep you from getting to low. It really just guarantees that you will miss any obstructions on the approach path if you are on or above the glide path. IMO a normal approach in most small single engine aircraft should be above the glide slope. I am sure others will disagree.

Brian
 
timwinters said:
They're way too low for me, but I do power off approaches. At my home 'drome, if I don't see four white when I turn final about 1/2 mile out then I'll likely need to add power to make the runway <fail>.
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+1 on that. Took a late night cruise to KPOU last night and thought "wow..I am more comfortable with the slightly steeper approach" especially at night and at an unfamiliar airport...

Just my preference as a low time 'noob!
 
Lessee how bad I am at math.

For a 3 degree glide slope, you are supposed to descend ~50' for every 1000' you fly forward, right? I figure that for a cessna 172's 9-to-1 glide ratio, you'd anticipate that you want to be on a glide path of AT LEAST the inverse tangent of 1 over 9, so something north of 6.34 degrees, to be able to make it to the runway. That is clearly above a 3 degree glide path.

Remember, however, that the vasi intercepts the runway at a point that is just before the aim point, which is usually 1000' down the runway. This means that if you're on the glide slope and you lose your engine at least you have an extra 1000' to play with. I'm sure I can figure out how close you have to be to the runway when your engine dies on the VASI to still make the threshold but SQUIRREL!
 
Yeah, during training my instructor would squawk loudly that I was too low... I had a red/white indication from the lights. Now the only time I really worry about the lights is landing at night; I can still hear him saying, "Red-red means you're dead".

Better to be a little high than a little low. There are several things you can do to lose altitude on final if you're too high, engine or not. There's only one thing you can do to stretch the glide, and that doesn't work if your engine is no longer making power.
 
This is good to know. I am constantly fighting to keep red over white even when I am on 2 mile final. I am going to go back to what is comfortable to me.

Thanks.
 
Two whites is just fine. Use the bug-splat method to determine if you will make the runway.

Two reds is not good.

My short field landings are consistently smoother with a steeper lower-power approach.

Yes, you need more than 6 deg to make a power off approach in a 172 with no flaps. Add flaps and it's even steeper. It's WAY steeper in a 182.
 
Yeah, has nothing to do with making the runway in the event of engine failure. It's just an aid to clear obstacles on final.

Flying FW at night I'm either on or slightly above. Flying RW, forget about being on. I'm coming in at around 6-7 degrees and 100 kts. If the engine fails I'm usually good within a mile of the runway.
 
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With PAPIs, target is 3 degrees. When the last light turns red, you are supposed to have at least 1 degree clearance above the highest obstacle with in 10 degrees either side of runway center line. If that isn't the case, then the obstacle has to be removed or the PAPIs have to be aimed higher. The PAPIs on Rwy 7 at Russellville (KRUE) are at 3.25 degrees because of an obstacle which has since been removed. The lights would be very easy to adjust back to 3 degrees but if that means they would have to be flight checked by the FAA, which now costs money, they are just going to stay like they are.
 
SixPapaCharlie said:
Is it designed to be an angle at which you should be able to make the runway or is 3 degrees (I think that's it) specified for a different reason?
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3 degrees, more or less, and it's optimized for best chance on an instrument approach. Pilots flying visually without any guidance tend to make about a 4-5 degree glide path to the runway, although even that is probably too shallow for gliding if you lose the engine as you turn final. Staying in position to make the runway after engine failure on final in landing configuration has not been part of either the PTS of any FAA guidance for at least 40 years.
 
Does that mean if you fly a white/white final approach on a checkride they'll bust you?
 
dans2992 said:
Does that mean if you fly a white/white final approach on a checkride they'll bust you?
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No, but if you fly red/red and don't correct, they might. PTS says nothing about altitude in the descent and landing phases (but it does about TPA). There is a special emphasis area for CFIT, which could be an issue for red/red, and it's an automatic fail if the examiner has to take control of the aircraft to maintain safety of flight (could happen for red/red).

You might get questioned about it, but you need to know what 14 CFR 91.129(e)(3) says anyway.
 
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If you are that frightened of your engine why did you leave the ground in the first place?
Yeah, I'm being sarcastic.
Gliding range has nothing to do with approach aids such as VASI, PAPI, and ILS.
You don't fly a Glasair, or a Baron or a P-Navaho or a P51 by cutting the engine on downwind - or if you do, better be a Bob Hoover.
 
Owad1971 said:
+1 on that. Took a late night cruise to KPOU last night and thought "wow..I am more comfortable with the slightly steeper approach" especially at night and at an unfamiliar airport...

Just my preference as a low time 'noob!
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At night, if you have a glide path reference available it is in your best interest to use it.

Otherwise, use your altimeter for a little reference and fly a normal pattern.






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SixPapaCharlie said:
This is good to know. I am constantly fighting to keep red over white even when I am on 2 mile final. I am going to go back to what is comfortable to me.

Thanks.
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Silly advice but if you fly a plane with a lot of flap be sensitive to and aware of flap failure and go around if you experience it on short final.
 
Ron Levy said:
3 degrees, more or less, and it's optimized for best chance on an instrument approach. Pilots flying visually without any guidance tend to make about a 4-5 degree glide path to the runway, although even that is probably too shallow for gliding if you lose the engine as you turn final. Staying in position to make the runway after engine failure on final in landing configuration has not been part of either the PTS of any FAA guidance for at least 40 years.
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Ron, I made a similar comment on a different forum and was asked what if anything in writing backs that up (besides the PTS). Or maybe more importantly is there some official documentation on any studies that led to the FAA's change of heart on that.
 
gismo said:
Ron, I made a similar comment on a different forum and was asked what if anything in writing backs that up (besides the PTS). Or maybe more importantly is there some official documentation on any studies that led to the FAA's change of heart on that.
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You'd have to go back 40 years to find the documentation for the FAA's change of philosophy from power-off to partial-power stabilized approach for normal VFR traffic pattern operations, and that means you won't find it on the internet. You'd probably have to dig through filing cabinets full of paper in the basement at 800 Independence Ave. But there is plenty of documentation in AC's, handbooks (like the AFH), pamphlets, etc, which makes the FAA's philosophy on this clear even if it doesn't include the data analysis which led to that philosophy.
 
Owad1971 said:
+1 on that. Took a late night cruise to KPOU last night and thought "wow..I am more comfortable with the slightly steeper approach" especially at night and at an unfamiliar airport...

Just my preference as a low time 'noob!
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Same here, went there last Thursday and thought the same
 
Dr. O said:
You don't fly a Glasair, or a Baron or a P-Navaho or a P51 by cutting the engine on downwind - or if you do, better be a Bob Hoover.
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When I first went to work at O'Reilly back in '94 our corporate bird was a p-baron. Our pilot used to fly power-off approaches all the time when VFR. Then he'd look over at me, grin and say, "people say that can't be done".
 
Ron Levy said:
You'd have to go back 40 years to find the documentation for the FAA's change of philosophy from power-off to partial-power stabilized approach for normal VFR traffic pattern operations, and that means you won't find it on the internet. You'd probably have to dig through filing cabinets full of paper in the basement at 800 Independence Ave. But there is plenty of documentation in AC's, handbooks (like the AFH), pamphlets, etc, which makes the FAA's philosophy on this clear even if it doesn't include the data analysis which led to that philosophy.
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Sounds like decision for the airlines. I chop off the power before final. I trained at an airport with no VASI/PAPI or whatever. I never even look at the VASI unless I happen to notice it.

When I checked out for my complex endorsement. we were 2,000' above pattern altitude when turning final and the task was to hit the numbers.
 
bartmc said:
Sounds like decision for the airlines. I chop off the power before final. I trained at an airport with no VASI/PAPI or whatever. I never even look at the VASI unless I happen to notice it.

When I checked out for my complex endorsement. we were 2,000' above pattern altitude when turning final and the task was to hit the numbers.
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Yea I was telling Bryan today via text that I really dont care what the VASI/PAPI is telling me as long as my sight picture is favorable and my speed is where it should be. I like to be high anyways as I really like to be conservative.... and my 235 sinks fast when I go to idle and throw a slip or two in so it doesnt hurt to be a little high.

I can see though, why it would be benificial during a night landing and probably will start using them for that purpose.
 
Ron Levy said:
You'd have to go back 40 years to find the documentation for the FAA's change of philosophy from power-off to partial-power stabilized approach for normal VFR traffic pattern operations.
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This was my biggest catch-22 during my primary training. Everyone always says be able to make the runway in the event of engine failure, but by definition, you can't if you use the FAA approved approach. Especially from the back corner when you turn base to final. No engine? No runway.

I know, the engine is much more likely to go kaboom on departure vs approach, but....
 
I'm sure someone more knowledgeable will pipe in, but I was told that the Vasi and other visual aids for slope are set up for heavy metal, fast planes and to fly approach higher than red over white. I used to find that white over white with one just beginning to change to red was just about right.........
 
Jhernandez04 said:
.... and my 235 sinks fast when I go to idle and throw a slip or two in so it doesnt hurt to be a little high.
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The 235 has "safe glide" mode...it glides like a safe when slowed down. The slip is overkill (but I do it too just 'cause I like to see the runway out the side window).
 
Same with the Arrow Clark. Even more so with those gaping holes in the wings.
 
Muttley said:
The average GA pilot would be better spent worrying about a stabilized approach on speed, on glide path and on centerline.
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I agree completely if the pilot doesn't fly enough to to "reach the next level" of airmanship. A "power on" stabilized approach allows one to be far more sloppy and still escape unscathed than a "power off" approach does (which is still a stabilized approach when flown properly).

Slowly reducing the throttle to idle abeam the numbers, flying the pattern, and touching down within 100' of the numbers without touching the throttle again takes far more skill, airmanship and ingrains far more true understanding of the airplane/winds/slips/etc. than flying a stabilized approach ever could.

Muttley said:
You are way more likely to ball it up on the runway by crappy airmanship than the engine quitting.
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Again, I agree completely, and believe that "power on" stabilized approaches breed "crappy airmanship".

If one flies less than 50 hours or so a year then, yeah, it's probably best to fly stabilized approaches because the number of hours required to proficiently, consistently and safely execute a power off approach probably aren't being flown...unless one is an exceptional pilot.

But, if one is flying closer to 100 hours a year (or more) then regularly flying power off approaches allows you to develop a skill and a feel for your airplane that you otherwise wouldn't.

Back when I was working, and flying for my business, I was flying around 200 hours per year and many more some years. Flying that much allows you to get into an "airplane zen" that can't be achieved when flying only 50 hours a year. I used to call it "wearing the airplane". You become one. It's cool. I haven't been that way w/ 57D for nearly three years now...but it was a really, really cool place to be.

Flame away!!!
 
Clark1961 said:
The 235 has "safe glide" mode...it glides like a safe when slowed down. The slip is overkill (but I do it too just 'cause I like to see the runway out the side window).
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Yeah, but full deflection slips down to about 20' AGL are really fun!

Straighten, flare, land. (Almost as quickly as you read those three words!)

:thumbsup:
 
I would always find myself higher than I wanted to be when approaching KTRI, something about crossing the mountains just north of the field. I always found myself having to slip the Arrow onto the runway. On more than one occasion I got comments from the tower about a nice slip. The guy must have been a pilot.
 
timwinters said:
When I first went to work at O'Reilly back in '94 our corporate bird was a p-baron. Our pilot used to fly power-off approaches all the time when VFR. Then he'd look over at me, grin and say, "people say that can't be done".
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it sure can be, but not safely from 1000 AGL 3/4 mile abeam the touchdown point with the gear extended.
 
Per my CFI: VASI PAPI are designed for larger faster aircrafts hence the shallower angle in comparison to the slow cessna's.


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spdracer888 said:
Per my CFI: VASI PAPI are designed for larger faster aircrafts hence the shallower angle in comparison to the slow cessna's.


Sent from my iPhone using Tapatalk
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No. It's meant for crappy weather or night flying, where you may not be able to see the obstructions.

Some of them are placed 1000 feet past the threshold. Those are intended for airliners. But you can use them, too.

If there are two of them (as sometimes happens), you can use either, but I'd suggest the nearer one.

They should not be necessary in VFR conditions, but that doesn't mean they can't be used. You can be high (two white), but not low (two red).

Furthermore, 14 CFR 91.129(e)(3) requires you to use the lower bound at Class B, C, or D airports.
 
So that's what those things are. They're always white all the way down for me.

I thought they were there to light you up for pictures.

< for the humor impaired...just kidding>
 
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