I'll have to think about how to do that in X-Plane. No doubt the magenta diamond would be below the aircraft, by how many "dots" high we would be I'm not sure. I'll see if I can duplicate.
Does this math look right, for comparing a 3.2 degree glide slope with a 3.75 degree slope:
Ok. I think Garmin will let you use either the Jepp data base or theirs, the Garmin base. Look at the Jepp Chart I posted in # 34 above. Do you think that’s going to make a difference? Like if you have the Jepp data base, it will give you a constant 3.75 angle starting 4.5 miles out but if you have the Garmin data base it will give you the angle from HIKLO to JAMID and the change to 3.75 at JAMID.
Which data base do you use? Jepp or Garmin.
That's a good question. X-Plane uses the navigation database from Navigraph, which supplies monthly database updates to simulators of all sorts.
If it’s true that some Garmins do in fact give you a ‘two stage’ angle on the VDI that would be just a wrong thing to ever have done in my opinion. The thinking would have to have gone something like this. Ok, there’s this altitude at HIKLO and the altitude at JAMID. We want to give the pilot something to follow so he doesn’t maybe get a bit steep and have to level off before getting to JAMID so we’re going to give him the angle from HIKLO at 6000 to JAMID at 4800. Then, when he gets to JAMID we’re going to change it to this 3.75 degree VDA angle thing. 1.6 miles from the Runway on an Approach with a 1 mile Visibility Minimum. It’s been changed to 1 1/8 now btw and was always 1 1/4 for Cat C.
.
Yeah, it’s not a big angle change. And we don’t really know for sure Garmin does it. But there are some clues they do/did. If so, it just doesn’t make sense to me. It nullifies the whole concept of why VDA was invented in the first place. Constant Angle of Descent down to the runway. Why change the angle. Even though it doesn’t “…present a serious challenge for a proficient pilot…” why test that proficiency? Is there anything to be gained by the vertical dogleg thing at the Step Down Fix? Anything? I can’t see it.Well, I think this gets into a very subjective topic. I won't argue with your viewpoint, but here's mine.
With a 90 kt ground speed on this approach the descent rate to trace a straight line from HIKLO to JAMID is 522 fpm. That increases to 597 fpm after JAMID. See the image of a typical VSI gauge below for context. I've photoshopped in copies of the needle at about 520 fpm and 600fpm.
I've flown enough instrument approaches (both practice, and in IMC) to know that when you throw in the effects of turbulence and varying wind speed and direction during the approach, going from 522 to 597 is not all that much of a change. Although your goal is to achieve an average descent rate that's correct, the gauge may be fluctuating +-100 fpm or more the whole time.
In summary, my take on this is that the change in angle is not large enough to present a serious challenge for a proficient pilot. I also agree that a constant rate would still be preferable.
But again, this is a very subjective topic and others will have different opinions, and that's okay with me too. It's not like I've never been wrong before
View attachment 106957
I agree that the angle change is small. Just a clarification on terminology (and Gryder made this error also)... the FAA does not term this "constant angle of descent" but rather "Continuous Descent Final Approach" (FAA AC 120-108). One could argue that continuous descent does not necessarily mean constant angle.
Ok. The correct term is Continuous Descent Final Approach. I’m all ears to listen to the argument about how that somehow results in other than a constant angle.
@luvflyin ... I think the "continuous descent" term is being used by the FAA to differentiate that strategy from the traditional "dive and drive" (i.e. descend, hold altitude, descend, hold altitude, etc). We could have different descent angles for each segment of a multi-stepdown approach, yet never actually level out and hold altitude... and that would still be a "continuous descent".
Just read it. The key point reference what we’ve been discussing here about how Garmin may display it on the VDI is:
1. Nothing requires the step-down fix. They could have made the MDA 4800 and just let it go at that. But there was a way to get a lower MDA by establishing the Fix with a Minimum Altitude and get a lower MDA.
I can confirm that. I am responsible for keeping the database up-to-date in the G1000 plane based at my CAP squadron, and we recently switched from Jeppesen to Garmin for our database subscriptions. (I don't know why.)
I was just asking is are Continuous Descent and Constant Angle somehow different. We already know what ever you name it, it’s the alternative to dive n drive.
Ok. Got it. If you start descending and you don’t stop and level off you are CDFA. And yeah, you can change your rate and angle during the descent and still be ‘continuously’ descending. Let’s throw Stabilized Approach into it. Stabilized Approach is the thing this whole CDFACANPAVDA thing is trying to achieve. Don’t you big iron guys have some kind of rule that if you don’t have it dialed in long before 1.6 miles from the runway, it’s go around time?
Yeah, rate will change on a constant angle as speed changes. Let’s take rate of the discussion other than it better not be more than a thousand. I’m talking about the pros and cons of these examples
I just said it would only be required to get an MDA lower than 4800. So they did throw it in. Not for grins but to get a lower MDA.
I’m not saying it’s necessary to get a lower MDA. I just said that the step-down is necessary to get a lower one. There is an obstacle there that requires descent to not go below 4800 until passing it. If a Fix can be put there to identify when past it then cool, put the Fix there and now you can go lower.
Yes. That has been discussed here in the past. The guy has always been a narcissistic prick from what I hear. He’s just taken the act online to feed his ego. But shoot that’s like 95% of the yOutUbers. Just don’t watch his videos. Problem solved.
I kinda feel like maybe a lot of folks are thinking “holy crap! I’ve done stuff like she did before, somebody should do something!” When the only “something” that is needed, is what you just said.
I think that might be a good idea. Put it 4.5 miles out there where Jeppesen depicts the start of a VDA. But it wouldn’t surprise me if there was a TERP’s rule that precluded putting it that close. Unless Approach says cross HIKLO ‘at’ 6000, or you were already at 6000 when you got the Clearance, you can just cross it higher and give yourself a longer run on a 3.75 degree ride down the chute.
Yup. That be the golden rule. Are you seeing something here that anybody thinks differently?
Do the FMS's give you the same angle from the FAF to the step-down as the VDA after it?