Timed VDP

[DC8 Flyer]

The reason I thought you were replying to me is because I started the thread and you didn't quote anyone else.

Also, you can do whatever you like, but do you really think that inaccurate data increases SA? I think that it decreases it.

I guess I wouldn't call it inaccurate data. I pulled a quick example out off the top of my head to show the numbers and how the "long hand" version and the 10% rule can be fairly close. We can argue the difference in 45 seconds, but the fact remains, if you sit down and figure it out to the inch, it is all out the window as soon as your groundspeed changes. Calculating a point at which you start thinking more about going missed than continuing helps me personally, in getting the big picture. Maybe it doesn't work for you, thats fine, but maybe my method will help someone out. I never claimed it was dead on balls accurate, but simply a way to keep track of your progress along the final approach course relative to "glide slope" intercept.

I give myself a buffer in the time, because we do a config change before leaving the MDA for the runway, flaps 35 to 50, that takes a little bit to restabalize and get going down at the proper rate so waiting until the last second will leave you high and diving for the runway so I lead it a bit.

 

[Tref]

Personally, I believe this whole discussion can be made moot by eliminating the "dive and drive" non-precision approach in favor of a constant path angle type approach. These are safer and can help reduce CFIT accidents during the approach phase. I am in disbelief that my company still has not moved in this direction even though they keep promising that this change is "coming".

That's how we did it in the 400 (and the A330.) We were not allowed to fly level at the MDA. The MDA was treated more like a DA(H) and once you "touched" MDA you had to go around. It took a bit more planning, but I think it was much safer.

 

[Tref]

I guess I wouldn't call it inaccurate data. I pulled a quick example out off the top of my head to show the numbers and how the "long hand" version and the 10% rule can be fairly close. We can argue the difference in 45 seconds, but the fact remains, if you sit down and figure it out to the inch, it is all out the window as soon as your groundspeed changes. Calculating a point at which you start thinking more about going missed than continuing helps me personally, in getting the big picture. Maybe it doesn't work for you, thats fine, but maybe my method will help someone out. I never claimed it was dead on balls accurate, but simply a way to keep track of your progress along the final approach course relative to "glide slope" intercept.

I give myself a buffer in the time, because we do a config change before leaving the MDA for the runway, flaps 35 to 50, that takes a little bit to restabalize and get going down at the proper rate so waiting until the last second will leave you high and diving for the runway so I lead it a bit.

I guess I understand you a little better now. So you don't use it like a real VDP, ie. you can't desend before this point, but more of an "expect to be on the glidepath around this point, plus or minus a bit." Fair enough, but really, we're both still looking out the window for our primary cues. Wouldn't you agree?

 

[DC8 Flyer]

I guess I understand you a little better now. So you don't use it like a real VDP, ie. you can't desend before this point, but more of an "expect to be on the glidepath around this point, plus or minus a bit." Fair enough, but really, we're both still looking out the window for our primary cues. Wouldn't you agree?

Agree 100%. To be perfectly honest however, when it is down and the wx is right at mins for a non precision, I find it very hard to "visually" fly the airplane down without some sort of vasi/papi guidance. It has always been a weakness of mine, the whole runway in the window thing just doesn't work for me, so I have to use math, ie distance from the runway to make it "look" right. Hopefully my company will get the approval to start using the FMS's we have to their full potential, nice VNAV all the way to the runway!

 

[Tref]

Agree 100%. To be perfectly honest however, when it is down and the wx is right at mins for a non precision, I find it very hard to "visually" fly the airplane down without some sort of vasi/papi guidance. It has always been a weakness of mine, the whole runway in the window thing just doesn't work for me, so I have to use math, ie distance from the runway to make it "look" right.

I know exactly what you mean.

Hopefully my company will get the approval to start using the FMS's we have to their full potential, nice VNAV all the way to the runway!

It's the only way to fly! Or, you could have a Flightpath Trajectory Indicator on the PFD like in the Airbus. Then you can say, "gimme the bird." Works great every time.

 

[FL420]

Hopefully my company will get the approval to start using the FMS's we have to their full potential, nice VNAV all the way to the runway!

Many companies fly equipment capable of performing Constant Angle Non-Precision Approaches(CANPA's) but don't want the extra costs of initial and recurrent training in CANPA's for each pilot. You must also have approval in the OpsSpecs.

When the Wx is right down to minimum visibility you might find yourself doing more missed approaches doing a CANPA instead of a dive and drive approach. That is because the MAP on a CANPA is at DA(H) up to two miles from the runway threshold while the MAP on a dive and drive is usually at the runway threshold. A non-commercial operator flying a typical GA aircraft to a long runway has a better chance of getting aboard safely using the dive and drive when not constrained by a requirement to land in the touchdown zone from a stabilized approach.