An air carrier crew on a night visual to TPA Runway 36L; from a left downwind; misidentified the MacDill Air Force Base and turned toward Knight airport Runway 3 before realizing where they actually were. Chart and communications issues were involved.
Synopsis
An air carrier crew on a night visual to TPA Runway 36L; from a left downwind; misidentified the MacDill Air Force Base and turned toward Knight airport Runway 3 before realizing where they actually were. Chart and communications issues were involved.
Narrative
Prior to the TOD into TPA we briefed the approach to 36L expecting a visual approach backed up by the ILS. Referring the [commercial] chart; we read that if vectored over Macdill AFB; remain at 2600' over Runway 04 before descent is started below that altitude. After that statement; it reads Macdill AFB is 8 miles south of TPA. While on approach into TPA; we were given vectors to a left downwind approach for runway 36L. Once we called TPA in sight; we were cleared for the visual approach to Runway 36L; with further instructions to remain north of Macdill AFB. Recalling the statement from the chart page referring to the 8 miles; I then looked at the approach plate for 36L showing the outer marker (PINCY) to be 5.6 DME and the previous approach fix to be at 8.2 DME. We both agreed that as long as we stay between the two fixes; we would meet the requirements. While on downwind; we noticed runway lights ahead that appeared to coincide with that of Macdill. While in the base leg turn; Approach instructed us to turn to the numbers. I replied that we were in fact in the turn at that time. Once rolled out onto base; we then could see that Macdill AFB was actually in front of us. At that time Approach again replied to turn toward the numbers. The Captain then began to turn toward the approach end of the runway and had descended to about 2200' while abeam Macdill. Once on the ground we were given a number to call. I discussed the train of thought with the Controller as well as what led us to believe we were north of Macdill. The reason leading to this confusion has to do with the 8 mile statement on the chart page; the light gray scale reference point of Macdill AFB on the approach plate and misinterpretation with the instructions 'turn toward the numbers'. The 8 mile statement alone with cross reference of the approach plate fix distances lead us to believe we were well north of Macdill. Looking at the approach plate; Macdill did not stand out being in a small gray scale color. In addition; the Controller's statement; 'turn toward the numbers;' was confused with; 'start your turn toward your approach final in order to prevent any further travel south.' With the false sense that we were north of Macdill; the Captain began his descent to intercept the GS putting us below the 2600' requirement while abeam Macdill AFB. The Captain and myself rarely fly into TPA which led to the uncertainty of the location of Macdill AFB. I would suggest modifying the way the chart page reads in reference to distance from TPA to Macdill. There needs to be a reference from the FAF or something that gives pilots a quick distinctive reference without the possibility of misinterpreting distance from Macdill. Macdill's location on the approach plate could be enhanced. Simply knowing 'turn toward the numbers' means go direct to the approach numbers would have been helpful.
Second reporter narrative
On downwind for runway 36L - took the visual and told to stay north of Macdill. First Officer checked chart page and noted that we should stay inside of 8 miles from TPA. We misidentified a runway in front of us as Macdill - turned north of that runway and set up for a final intercept just south of PINCY (OM) that would put us at 7 miles from Runway 36L. As I turned base; ATC said; 'turn towards the numbers'. That was stated just as we started our base turn - so we thought our position was OK. I descended from 2600' to 2100' to capture the glidepath at PINCY. As we started the dogleg ATC again said; 'turn towards the numbers.' I then saw Macdill just off our right. I misidentified a runway on downwind as Macdill. Thought; 'turn towards the numbers;' was a call suggesting turn towards the final. Chart stated to stay within 8 miles of runway 36L. I should have more closely viewed the light colored picture of Macdill on the 36L approach plate. Should have stayed at 2600 feet and made a tighter base turn directly to the outer marker - then dropped down to 2100 feet to safely capture glideslope intercept altitude. Adjust chart page to state; 'stay North of Macdill - which is abeam ..... (the fix 3 miles from the outer marker).' The 8 mile statement lead us too close to Macdill.
NASA callback
The reporter stated that several issues lead to their confusion and the error. The first issue was the statement about remaining inside of 8 DME and north of Macdill. As they were on the left downwind in the turn toward the airport they may have initially lined up with Knight airport; northeast of Macdill; which would have taken them almost directly over Macdill but within 8 DME of TPA as they lined up on Knight Runway 3. The second was misidentifying Macdill and TPA. There is some confusion with this issue but for certain the crew was not looking initially at Macdill and did not identify it until they were turned directly toward TPA. The Air Carrier commercial chart page wording was confusing and the commercial approach plate for TPA ILS Runway 36L shows Macdill as a small gray complex; when in fact it is a large facility. Finally; the Controller's statement; 'Turn to the numbers;' was not taken as meaning; 'turn toward Runway 36L.' The crew was not certain what was meant.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.