power on final changes aiming point?

[kwc98]

I am having a little bit of a hard time wrapping my head around this:

I am on final and perhaps I am a little high(altitude), speed is good, aiming point good, so I walk out the power a bit. The speed of the plane remains the same, but I descend a little steeper than I was. Here is the question:

Does the aiming point move up, since I am now descending faster. Logic tells me it should, but I am not so sure. I am understanding pitch for speed and I see how removing power increases my descent, but for approach on final, I am not sure of the other items that may be changing as well.

thanks,
Ken

 

[dtuuri]

I've never been one to teach by using a spot on the windshield as a gunsight. It changes with wind, for example, all other factors the same. Yes, with less power, the nose must pitch forward to keep the same speed, so the aiming point on the runway will move up as framed in the windshield. CFIs who put an aiming mark on the window lead students into making low and slow approaches using such technique or flying way too fast at the threshold.

dtuuri

 

[flyingron]

The spot on the windshield is highly affected by pitch which unless you're rock solid on your approach is going to change. You need to just interpret where you think the airplane is approaching by other means. The spot on the window works well in what is supposed to be constant attitude (like steep turns, etc...).

 

[bullwinkle]

You have to judge your approach angle, speed, and sink rate. There is a lot going on during the approach.

Instead of an aiming "point" try looking at where the landing zone is in your sight picture. If it's moving up, you are sinking relative to the current glideslope and the point you will touch down is moving closer to your airplane. If it's moving down, the touchdown point is moving farther away. If it's not moving, you have a steady approach.

As FlyingRon said, this only really works if your pitch doesn't change. A lot of this is done by feel.

 

[warthog1984]

I am having a little bit of a hard time wrapping my head around this:

I am on final and perhaps I am a little high(altitude), speed is good, aiming point good, so I walk out the power a bit. The speed of the plane remains the same, but I descend a little steeper than I was. Here is the question:

Does the aiming point move up, since I am now descending faster. Logic tells me it should, but I am not so sure. I am understanding pitch for speed and I see how removing power increases my descent, but for approach on final, I am not sure of the other items that may be changing as well.

thanks,
Ken

If you are on final and pull power, the glidepath (and therefore the aiming point) will move down. However, if you are looking for the point that doesn't appear to move in your vision; you have to wait to stabilize at your new, steeper descent profile before it becomes meaningfully.

 

[DGlaeser]

The 'spot' (area) that doesn't move is your aim point - but where it is on the windshield is affected by pitch (as noted already). Sounds like you have things pretty well figured out, even if you can't explain it.

Watch the spot you want as your aim point, wherever it is on the windshield, and observe if it is moving or fixed. Then find the spot that doesn't move, and decide if that is OK or not. If not, adjust as needed.

Don't fixate on where it is on the windshield, just observe the 'spot' on the ground (runway) that isn't moving. After a few times doing that, it will become the natural thing to do, and your observation will become independent of pitch attitude.

 

[midlifeflyer]

I've never been one to teach by using a spot on the windshield as a gunsight. It changes with wind, for example, all other factors the same. Yes, with less power, the nose must pitch forward to keep the same speed, so the aiming point on the runway will move up as framed in the windshield. CFIs who put an aiming mark on the window lead students into making low and slow approaches using such technique or flying way too fast at the threshold.

dtuuri

FWIW, I'm with you in a dislike for the "spot on the window" technique. In addition to what you mentioned, I think it's conducive to developing a fixation habit and other errors.

Note that even the question being discussed is centering on where the spot is supposed to be and how it is supposed to move rather than where the aircraft is supposed to be and how it is supposed to move.

 

[Henning]

I am having a little bit of a hard time wrapping my head around this:

I am on final and perhaps I am a little high(altitude), speed is good, aiming point good, so I walk out the power a bit. The speed of the plane remains the same, but I descend a little steeper than I was. Here is the question:

Does the aiming point move up, since I am now descending faster. Logic tells me it should, but I am not so sure. I am understanding pitch for speed and I see how removing power increases my descent, but for approach on final, I am not sure of the other items that may be changing as well.

thanks,
Ken

The point on the ground you are aiming at should sit steady in your windshield. If it appears to rise, you are falling short and need to add throttle. If it is going down in the windshield you are overshooting and need to reduce power if possible, slip, or go around. Where exactly something is in the windshield isn't that important, it's whether it's moving or not. I usually aim for just short of the threshold.

 

[poadeleted20]

I am on final and perhaps I am a little high(altitude), speed is good, aiming point good, so I walk out the power a bit.

Proper response.

The speed of the plane remains the same, but I descend a little steeper than I was.

...and the nose drops slightly, too, in order to maintain the same AoA (speed) with a steeper glide path.

Does the aiming point move up, since I am now descending faster.

Initially, it will -- not because you're descending faster, but rather because your attitude pitches very slightly down to maintain the same speed on a steeper glide path. Further, as you continue with a flight path now intersecting the ground closer to you, the original aim point will continue to move up. Then, when you reach the glide path you want, you add power again to shallow your descent so your flight path once again goes to your desired aim point. At that point, the plane will pitch slightly up and the aim point will move slightly down, but then stabilize where it is if you have the power set properly for that desired glide path.

 

[nosehair]

I am on final and perhaps I am a little high(altitude), speed is good, aiming point good[\QUOTE]
If your aiming point is good, why do you think you are high. The perception of being high comes from the aiming point to appear to move down or back beneath the nose. That's why you reduce the power, so you can pitch the nose down to stay on the aiming point.

 

[kwc98]

Thanks for all of the information. Someone mentioned that perhaps I was fixated on the aiming point, this was pretty true I think. Last night I had the best landing for touch and goes to date. I had the CFI do 2 landings to try get a better sense of feeling the flare and I 'got' the aiming point in final, but looked at everything as I came down, alignment, speed, slope. Not all were perfect, but CFI indicated they were safe!

Soloing soon, thanks,
Ken

 

[bullwinkle]

Great Ken, good luck!

 

[Henning]

Thanks for all of the information. Someone mentioned that perhaps I was fixated on the aiming point, this was pretty true I think. Last night I had the best landing for touch and goes to date. I had the CFI do 2 landings to try get a better sense of feeling the flare and I 'got' the aiming point in final, but looked at everything as I came down, alignment, speed, slope. Not all were perfect, but CFI indicated they were safe!

Soloing soon, thanks,
Ken

Cool, remember that your aim point shifts in the round out to the end of the runway. Even when the nose comes up and blocks the view, that is still where your eyes should be pointing. Take whatever flying cues you need from your peripheral vision, but keep your eyes pointed for the end of the runway. Where the eyes look, the body will follow. A corollary to this is 'Never focus on what you want to avoid or you will hit it.' Always watch the path you want to follow.

 

[petrolero]

The spot on the windshield is highly affected by pitch which unless you're rock solid on your approach is going to change. You need to just interpret where you think the airplane is approaching by other means. The spot on the window works well in what is supposed to be constant attitude (like steep turns, etc...).

Agree.

The aim point thing only remains constant while you are on a straight-line path to that point on the runway.

If you are high and you descend straight-line (steeper angle) to that runway point you can use the spot-on-the-windshield just fine. You are stabilized but coming in steeper.

But if you are high (4-white PAPI) and decide to go down to the 2-red 2-white path on a PAPI, you can't really use the spot-on-windshield reference during the transition from high path to lower path. Once you get down to the 2-red 2-white path and get stabilized then you can begin using the wishshield spot thing again.

It only works while you are stabilized and, conversely, it is a great way to determine if you are stabilized.