DA40 Diamond Star
Flight Crew Instrument; Flight Crew Private; Flight Crew Sea
Flight Crew Last 90 Days 25; Flight Crew Total 568; Flight Crew Type 513
Communication Breakdown; Confusion; Training / Qualification
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Human Factors; Procedure
I was receiving vectors to final for an ILS approach. Approach clearance call was something like: 'Fly a heading of 250 to intercept the localizer. Cleared ILS 29R circle to land 11L. Maintain 2;000 FT until established on the localizer.' No mention was given to intercepting the glideslope; or being established on the ILS. Conditions at that point were visual except for a small cloud between me and the airport. Upon intercepting the localizer (laterally); and being in visual conditions; my thinking was that I was cleared to descend at my discretion since no mention was made to intercepting the glideslope. I assumed that the Controller was aware I was in visual conditions; and I had always previously been cleared for an ILS approach with wording such as; 'Maintain 2;000 FT until intercepting glideslope'; or 'Maintain 2;000 FT until established on the ILS'. After a brief descent; Controller asked me to state my altitude; which at that time was 1;800 FT. He told me entry to the approach was at 2;000 FT. I affirmed back that I was correcting; and climbed back up to 2;000; at which point I was then a bit above the glideslope. This then caused a more rapid attempt to correct back to glideslope; with a brief overshoot; prompting a low altitude warning from the Controller. This was also rapidly corrected; at which point the Controller handed me over to Tower.Confusion arose due to the language of; 'Maintain 2;000 FT until established on the localizer'. While I know that I was cleared for the ILS; which means maintain the glideslope; during that process-intensive phase of flight; I just jumped to assume he meant established on the localizer to mean just that-laterally on the localizer (as the localizer provides no vertical guidance). A more precise phraseology; such as; 'Maintain 2;000 FT until established on the ILS'; or 'maintain 2;000 FT until established on the localizer and intercepting glideslope' would be more intuitive and prevent such erroneous thinking.
DA40 pilot reports being confused when cleared for the ILS and to maintain 2;000 FT until established in VMC and starts descending before glideslope intercept.