I am examining various RNAV departure procedures and especially those whose purpose is to overlay the existing conventional ones. I noticed that some of them begin with a "Flight at Altitude" instruction, immediately followed by either a DF or CF leg which end at a Waypoint very close to the associated airport. As a consequence, an aircraft whose initial climb gradient is small enough will reach the specific altitude well after it has passed the aforementioned waypoint and as a result, if the CF/DF leg must be followed, it must fly backwards in order to comply.
Take, for example, ANEKI9F overlay departure procedure of Frankfurt Airport. The respective conventional procedure is charted as follows:
Below I provide its equivalent description, as it is included in Eurocontrol's AIP library for German procedures:
Eurocontrol Charts AD 2 EDDF 5-7-34. ANEKI NINE FOXTROT:
On RWY track to 4.5 DME FFM/1.5 DME FRD or 800, whichever is later; LT (MAX IAS 210 KT until established on R356 RID), on R356 RID to RID (); on R183 RID to ANEKI ().
GPS/FMS RNAV: [A800+] - DF134 (25C)[L] / DF135 (25L)[L] - DF141 (25C) / DF142 (25L) - DF143[L] - DF137[K 210-; R] - RID[R] - ANEKI.
The problem is that fixes DF134 and DF135 are near runway's end. As a result, if the aircraft climbs even with 500ft/NM, it will still fly over those fixes. Or in other words, the aircraft will reach those fixes well before it climbs at 800ft.
My question is, which of those two instructions has priority? If the aircraft reaches DF134/DF135, will the "Fly at Altitude 800ft" order be negated and the aircraft will fly at the next waypoint (DF142/DF143) or should it ignore the initial waypoints (DF134/DF135) and keep climbing until it reaches at 800ft altitude and then fly at the next waypoints (DF142/DF143)?
If someone could point me in the right direction I would highly appreciate it.
EDIT: As J. Houggard aptly stated, an assigned adverse minimum climb gradient should exist for preventing this conflict from taking place. However, no such climb gradient is assigned, according to the following table (source: Eurocontrol AIP Library).
Even if the table implies that the assigned climb gradient of CINDY1F procedure also applies to ANEKI9F (315ft/NM), it is still not enough.