Narrative:

[We were] flying the ILS runway 23 approach to fdk in good VMC as part of instrument proficiency training. Reporter/pilot flying [was] in the left seat; under the hood; [an] experienced CFI-I [was] in the right seat. Time and distance to the NAVAID are roughly accurate; but neither made note at the time. There were several aircraft practicing the ILS 23; and more doing general pattern work. All aircraft on the ILS; ranging in type and speed from a C-172 to a uh-60 helicopter; were self-announcing and doing a good job of coordinating locations to avoid conflicts. While flying with the localizer and glideslope needles centered; instructor/pilot not flying exclaimed 'wow!' reporter/pilot flying looked up and saw a columbia flying at the exactly same altitude and approximately 10 off our left wingtip; overtaking us at surprisingly high relative velocity (we were at 90 KTS IAS at the time to avoid overtaking aircraft ahead). We took no evasive action; as the columbia was already abeam and pulling ahead rapidly when it was spotted. The columbia made took no evasive action; and continued on the ILS as if unaware of the near collision. Both reporter and instructor remarked; almost simultaneously; 'I've flown this close to another aircraft before; but we were in formation.' both reporter and instructor are experienced pilots; and each believed he had a good mental 'picture' of the location of other aircraft operating in the pattern and on the ILS 23 approach. The columbia simply wasn't 'on the (mental) radar' because he had not announced his presence. The only announcement the columbia was heard to make on the CTAF was to later report 'columbia on a 1 mile final on the ILS 23 at frederick'. Our most charitable guess was that perhaps the columbia had been on another frequency and didn't tune into the CTAF soon enough to be aware of the multiple aircraft also flying the same approach at the same time. Certainly we and other aircraft had made position reports frequently enough and accurately enough (GPS equipped) that the columbia's pilot should have been aware that he was flying at high speed on an approach with several slower aircraft already established ahead of it. Yet the columbia did not appear to be aware of our presence at any point; and it approached us from a blind area. This could very easily have resulted in a fatal collision. At any uncontrolled field; especially one that is as busy as fdk on a rare warm; sunny; winter day; it is essential to establish situational awareness early and make others aware of your position and intentions; lest two aircraft attempt to occupy the same space simultaneously.

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Original NASA ASRS Text

Title: A Columbia aircraft approached FDK on the Runway 23 Localizer without reporting on CTAF frequency. This resulted in a NMAC with another aircraft conducting a practice ILS 23. The Columbia may have been on a PCT frequency until short final.

Narrative: [We were] flying the ILS Runway 23 approach to FDK in good VMC as part of instrument proficiency training. Reporter/pilot flying [was] in the left seat; under the hood; [an] experienced CFI-I [was] in the right seat. Time and distance to the NAVAID are roughly accurate; but neither made note at the time. There were several aircraft practicing the ILS 23; and more doing general pattern work. All aircraft on the ILS; ranging in type and speed from a C-172 to a UH-60 helicopter; were self-announcing and doing a good job of coordinating locations to avoid conflicts. While flying with the localizer and glideslope needles centered; instructor/pilot not flying exclaimed 'Wow!' Reporter/pilot flying looked up and saw a Columbia flying at the exactly same altitude and approximately 10 off our left wingtip; overtaking us at surprisingly high relative velocity (we were at 90 KTS IAS at the time to avoid overtaking aircraft ahead). We took no evasive action; as the Columbia was already abeam and pulling ahead rapidly when it was spotted. The Columbia made took no evasive action; and continued on the ILS as if unaware of the near collision. Both reporter and instructor remarked; almost simultaneously; 'I've flown this close to another aircraft before; but we were in formation.' Both reporter and instructor are experienced pilots; and each believed he had a good mental 'picture' of the location of other aircraft operating in the pattern and on the ILS 23 approach. The Columbia simply wasn't 'on the (mental) radar' because he had not announced his presence. The only announcement the Columbia was heard to make on the CTAF was to later report 'Columbia on a 1 mile final on the ILS 23 at Frederick'. Our most charitable guess was that perhaps the Columbia had been on another frequency and didn't tune into the CTAF soon enough to be aware of the multiple aircraft also flying the same approach at the same time. Certainly we and other aircraft had made position reports frequently enough and accurately enough (GPS equipped) that the Columbia's pilot should have been aware that he was flying at high speed on an approach with several slower aircraft already established ahead of it. Yet the Columbia did not appear to be aware of our presence at any point; and it approached us from a blind area. This could very easily have resulted in a fatal collision. At any uncontrolled field; especially one that is as busy as FDK on a rare warm; sunny; winter day; it is essential to establish situational awareness early and make others aware of your position and intentions; lest two aircraft attempt to occupy the same space simultaneously.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.