Undershoot Vs. Overshoot airport landing accidents

Le jeudi 18 avril 2019 15:36:08 UTC+2, Steve Leonard a écritÂ*:
On Thursday, April 18, 2019 at 8:12:20 AM UTC-5, Tango Whisky wrote:

Go and try that with a DuoDiscus.

Bert TW

But, only on a runway that is clear off the departure end. Because you will depart, right, Bert?

Steve Leonard

Well, you will float over the runway forever.
I always prefer a slip (which works extremely well in both ASK21 and DuoDiscus) - no change of attitude, and dosage is much easier.

But in the end, I prefer to train people to do a proper approach pattern, where you end up un final with 50% airbrakes.

Please don't teach the dive to lose altitude technique. The problem is total energy, simply the kinetic plus potential energy. Most pilots are trained with judgment on altitude (potential energy) but have poor judgment how speed (kinetic energy) will impact touch down point and speed. Our brains are much better at doing estimates with constant speed. Yes, it is a neat trick to dive at the ground but has a higher probably for error than simpler techniques. See the article in soaring about the pilot that flew off the end of the runway. If you are really high, 500 to 1000 feet agl, the glider polar works both ways around the best l/d, rather than speeding up it is better to slow down and use full spoilers and a slip. I have modeled both techniques and the achieved l/d over the ground is just as low with the slower technique and there is no speed to scrub once you are back in correct height band for the approach. If you are really high, slow down to near stall speed, use full spoilers and slip. As you get lower (about 400 feet agl) accelerate to normal approach speed for the conditions.

Even better is to teach students to be flexible and not get fixated on completing a traditional pattern, S-turns or a 360 if a pilot is really too high are better options.

On Thu, 18 Apr 2019 07:00:39 -0700 (PDT), Tango Whisky
wrote:

Steve Leonard

Well, you will float over the runway forever.
I always prefer a slip (which works extremely well in both ASK21 and DuoDiscus) - no change of attitude, and dosage is much easier.

100% agree.


But in the end, I prefer to train people to do a proper approach pattern, where you end up un final with 50% airbrakes.

.... not to mention that precise speed control is the thing that
counts.

It is absolutely necessary in an outlanduing, and in my humble opinion
ought to be trained in any landing, even if there''s a 6.000 ft
runway.

Cheers
Andreas

Bert, Would you accept an Arcus vs a Duo?

Yes. Anytime.

Lots of great insight to digest...Dive and Drag is an interesting solution, if you have enough runway to scrub off the excess speed and/or your spoilers are effective. My ASW19 stock spoilers are just not effective enough for me to try the Dive and Drag method.

Reverse Base Method = 180° turn to reverse + 90° turn to final = 270° (two turns & wind corrections).

Why not just make a stable, descending 270° turn when crossing the final? In powered, fixed-wing aircraft, it's not unusual to get assigned a right or left 270 to final by tower to improve spacing on departing aircraft. It's a basic ground reference maneuver that could be adapted for gliders so you roll out aligned with the runway.

We're supposed to be able to turn back to land above 200ft with a rope break, which is based on our collective understanding that we can safely execute a turn, maintain speed, and align with the runway from that minimum altitude. That requires 180° of turn, if the towplane drifted downwind and you turn into the wind (ideal, but our guys don't). Or, 210-270° total if you have to reverse course, angle for the runway, then turn back to align with the runway. The second scenario requires multiple, low-altitude turns. Is that ideal?

Performing a stable, 270° or 360° turn for altitude correction should be within out skillset, but only if the excessive altitude is above a certain threshold for your ship. 100-200ft high? Maybe not the best option. Clear knowledge of your ship's descent rate in a turn is critical for decision making.

That said, I've always been successful with a little slip to correct for any excess altitude. Starting the correction on the base leg and performing a slipping turn to final burns off a lot of excess altitude. (I learned to do this with Phil Beale on my CFI-A checkride back in 1986.)

Paul A.
Jupiter, FL

On Thursday, April 18, 2019 at 2:05:10 PM UTC-5, Tango Whisky wrote:
Yes. Anytime.

This isn't intended to come across as a "I told you so", but educational for those who predicted that a steep full spoiler approach will put you into the far fence at high speed.

Arcus M, 1650 lbs. starting out close to the same spot as the first video and also 1,200 ft MSL (field elevation 300) and I had to close spoilers almost fully to clear the 20' high power lines on the approach end of the "extension" at SCOH. I adjusted pitch just a tad and ballooned before touchdown but total distance over the 20' wires was approximately 1,400 ft and without significant braking my landing roll was on the order of 700-800ft per Google Earth.

I will try this again, but starting much higher and post again. With full spoilers and modest increase in airspeed you can scrub a lot of altitude. Recommended to be tested at altitude first.

Video at the following link:

https://youtu.be/2-KiGtSbkMA

Mark

Go and try that with a DuoDiscus.


Pfft.

https://youtu.be/Yc-oTfr5Zwc?t=525

What's your point? That was an easy situation.
How about you're too high on a field 700 ft long? 750 ft is about what I can expect as a field where I fly. And I've got away with 300 ft.

Bert TW

On Wednesday, 17 April 2019 09:28:44 UTC-6, wrote:
I always assumed that there are more overshoot airport accidents than undershoot ones. That is mainly due to our general knowledge that it's better to be too high than not high enough.
Am I correct here ?
Dan

Some good take-homes here that are generally true:

1. You are more likely to err and land short on airport landings.
2. You are more likely to err and land long or with too much energy on outlandings.
3. You can dump more energy with drag at high speed BUT...
4. This is very glider-dependent (i.t.o. your state at the threshold of runway)
5. Lengthening your glide path safely is easy BUT...
6. Not that easy to practice, depends on your home site.