C172 pilot reported a near midair collision due to congested airspace and radios.

Narrative:

While level at 4;000 feet on an instrument flight rules flight plan the aircraft I was flying had a close call with a low wing single engine aircraft positioned 1-2 o'clock approaching head-on at same altitude. I; the pilot did not hear any radio calls by approach control regarding this traffic conflict well in advance until the other aircraft was approaching very close off the right side of the C172. The other aircraft made a sharp left climbing turn to avoid my aircraft while I dropped the nose to lose some altitude. It happened so quickly as I saw the traffic probably approximately 200-500 feet horizontal separation coming right at me as my aircraft flew past by him or her nearly missing my tail area by a vertical separation estimating approximately 50-100 feet or so; respectively. About 2-3 seconds prior I saw the other aircraft quickly approaching me; approach was on the radio saying 'I was trying to give you traffic on somebody that just crossing on top of you; did you even see him?' at that point; I saw the aircraft really close from my position and replied back to approach I saw the traffic and that was a close one.' approach control frequency was congested and was blocked by multiple calls at times. Even though; I was flying a cessna 172L skyhawk with just basic flight instruments while IFR in VMC; I still need to have an effective visual scan in a highly concentrated airspace. Luckily a potential catastrophic event was avoided.

Original NASA ASRS Text

Title: C172 pilot reported a near midair collision due to congested airspace and radios.

Narrative: While level at 4;000 feet on an Instrument Flight Rules flight plan the aircraft I was flying had a close call with a low wing single engine aircraft positioned 1-2 o'clock approaching head-on at same altitude. I; the pilot did not hear any radio calls by Approach Control regarding this traffic conflict well in advance until the other aircraft was approaching very close off the right side of the C172. The other aircraft made a sharp left climbing turn to avoid my aircraft while I dropped the nose to lose some altitude. It happened so quickly as I saw the traffic probably approximately 200-500 feet horizontal separation coming right at me as my aircraft flew past by him or her nearly missing my tail area by a vertical separation estimating approximately 50-100 feet or so; respectively. About 2-3 seconds prior I saw the other aircraft quickly approaching me; Approach was on the radio saying 'I was trying to give you traffic on somebody that just crossing on top of you; did you even see him?' At that point; I saw the aircraft REALLY close from my position and replied back to Approach I saw the traffic and that was a close one.' Approach Control frequency was congested and was blocked by multiple calls at times. Even though; I was flying a Cessna 172L Skyhawk with just basic flight instruments while IFR in VMC; I still need to have an effective visual scan in a highly concentrated airspace. Luckily a potential catastrophic event was avoided.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1585890
Time
Date	201810
Local Time Of Day	1201-1800
Place
Locale Reference	DAB.TRACON
State Reference	FL
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	IFR
Aircraft 2
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Commercial Flight Crew Instrument
Experience	Flight Crew Last 90 Days 35 Flight Crew Total 580 Flight Crew Type 450
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 300 Vertical 50