JnsV wrote:
You misunderstood what I wrote.
Then I guess one of us misunderstood I believe Timothy. IIRC he wrote (in essence) that people shouldn’t substitute DME with GPS because it can kill them. It related to keeping old equipment instead of moving on. He didn’t argue (at least that I recall) that DME (or NDB) should be used in RNAV(GNSS) approach design.
But why a specific operator approval?
Martin wrote:
Then I guess one of us misunderstood I believe Timothy. IIRC he wrote (in essence) that people shouldn’t substitute DME with GPS because it can kill them. It related to keeping old equipment instead of moving on. He didn’t argue (at least that I recall) that DME (or NDB) should be used in RNAV(GNSS) approach design.
Possibly I just (mis)understood that kind of argument implicitly from the thread context around his post.
OK, let me be clearer.
That point was not about the use of NDB or DME in RNAV design. I believe that both are inherently wrong and should not be included in RNAV, RNP procedures.
My point was that fix substitution of GPS for DME is potentially confusing and is known to have killed people, most notably quite recently in Dundee.
For that reason, I would feel very uncomfortable flying or flying in an aircraft which was executing an approach which requires DME when there is no DME, and fix substitution is being used instead.
Is that better?
Substitution of GPS for DME ATD is not an issue in the US, because the distance the DME reads is referenced to the location of the DME antenna, not the runway threshold. The location of the DME antenna is also a named waypoint and the distance is the same, GPS or DME. Slant range is not a factor on an approach.
NCYankee wrote:
Substitution of GPS for DME ATD is not an issue in the US, because the distance the DME reads is referenced to the location of the DME antenna, not the runway threshold. The location of the DME antenna is also a named waypoint and the distance is the same, GPS or DME. Slant range is not a factor on an approach.
Yes, that is an issue in the UK….in the Dundee case that Timothy refers to, the DME antenna is set to read zero at the threshold but the antenna is actually 700m (0.4nm) after the threshold of Rwy09….who is what I think you mean….but that was not actually the problem…
I believe in this case the waypoint being referenced was the DND NDB which is nearly 3nm short of the threshold….if they believed the GPS distance was the distance to the threshold it explains why they descended too early and collided with high ground… (The plate for the NDB procedure references DME for the step-downs)
Timothy wrote:
My point was that fix substitution of GPS for DME is potentially confusing and is known to have killed people, most notably quite recently in Dundee.For that reason, I would feel very uncomfortable flying or flying in an aircraft which was executing an approach which requires DME when there is no DME, and fix substitution is being used instead.
Is that better?
Thanks, clear now.
My point was that fix substitution of GPS for DME is potentially confusing and is known to have killed people, most notably quite recently in Dundee.
That oversimplifies it. Discussed here:
http://www.euroga.org/forums/flying/5455-dundee-baron-crash-may-2015-accident-report#post_97415
Yes, of course it over simplifies it. But the fact is that if he had been using DME, as he should have been, he would be alive.
I can’t understand why those of you who own aircraft are so reluctant to carry an ADF box, they are light, reliable, don’t take much panel space and some of them even have Superflag output to make them safer for your EFIS systems.
