Windshears in the Navy’s Heavy

An E-6B Mercury comes in for a landing. (Photo courtesy of LT Mike Kelly)

BY LT MIKE KELLY, VQ-4

There’s an Irish blessing that ends with the saying, “may the wind be always at your back.” Luckily, I’m a few generations removed from the old country because that mindset doesn’t jive well when landing an E-6B Mercury, especially when that wind comes in the form of windshear.

In late August 2016, we took off from Tinker Air Force Base (AFB) for aerial refueling and dedicated fieldwork. Once complete with the A/R, we coordinated our return to Tinker. Forecasts predicted suitable conditions for VFR patterns; the TAF line had strong winds down the pipe and some cumulonimbus clouds. Knowing that life is a bit unpredictable in Oklahoma, we planned on Offutt AFB in Nebraska as our divert field option.

In the descent, we discussed spending 30 minutes in the visual pattern. Circumnavigating some isolated storms, Tinker AFB ATIS reported nothing alarming at the field: minimal crosswinds and VFR. The flight engineer then said that another crew from our squadron had just called windshear over the maintenance frequency, and had gone around twice.

Over the maintenance frequency, the other crew’s aircraft commander (AC) said they landed successfully on the third approach after starting on RWY13 and switching to 36. The aircraft commander reported a 20-knot tailwind on final for 36 before it shifted at 800 feet AGL. He also stated that the air was increasingly turbulent north of the field.

Cleared for the visual, we discussed doing a touch and go if the winds were stable, but the air became consistently turbulent through 5,000 feet MSL. I then briefed a flaps 50 full stop, adding that we would execute a go-around if we encountered any indications of windshear. We would have 29,000 pounds of fuel beginning the first approach and briefed 27,000 as our bingo for heading to Offutt, anticipating 17,000 pounds overhead Offutt (NATOPS minimum shutdown fuel for the E-6 is 10,000 pounds). Offutt was forecast to be VMC with a strong potential for dodging storms en route.

We intercepted a five-mile final as the KC-135 we tanked off of was on the landing rollout. Tower shared that they reported windshear at 800 feet AGL. We continued.

Windshear is a regular discussion topic at oral boards as well as quarterly simulators. In sims, we would recognize erratic airspeed preceding sudden airspeed and altitude loss. I had never trained toward recognizing those instrument indications in heavy turbulence. We stress the dangers of sudden airspeed losses in a heavy jet low to the ground. But rolling out on final, my confidence was high: Two planes just got in, we have a senior flight engineer, an AC as my co-pilot, and I’m an instructor. We’ve got this. We’re getting in.

On final, we had moderate to severe turbulence and a steady 25 knot tailwind. We added the maximum allowable increment for potential windshear, 20 knots, to our 125-knot reference speed. The field was calling winds 010/9G19. Approaching 1,000 feet AGL the tailwind died and shifted. Coming through 1,000 feet my co-pilot said, “There’s the windshear,” and my flight display lit up with an amber “WINDSHEAR,” indicating increasing performance. As increasing performance can precede a decrease, we knew to go around below 1,000 AGL. I called “Go around” and fed in power, the FE tweaking the final setting. The co-pilot called flaps 25 and moved the lever. I reflexively thanked him, even though I knew before calling the go-around that I wanted to hold configuration until climbing.

During the go-around it was difficult to read my instruments and maintain the desired attitude, but after a few moments we began to climb with slowly increasing airspeed. Knowing PIREPS north of the field reported turbulence, we asked for an immediate crosswind turn, and I limited bank angle to below 15 degrees for the turn. Everybody stated they were good for another approach. I briefed maintaining configuration until steadily climbing. I intercepted a four-mile final and rode the tailwind through heavy turbulence. The FE informed us that we were “min fuel,” which limited us to eight degrees nose-up, 10 down. At 800 feet AGL we got the amber WINDSHEAR, immediately followed by a red alert and an aural alert, “WINDSHEAR! WINDSHEAR!” With 145 set as our approach speed, we saw airspeed yo-yo between 170 and 130. We began sinking. The flight data would later show we reached fuel flow of 8,900 pounds per hour on all four engines during the go-around.

With the turbulence, I’m not sure how low we went. I don’t think it was below 700 feet. The Mercury in a low fuel state usually exhibits excellent climb performance with high thrust settings on the motors. But this climb was very different. The jet was abnormally slow to respond. Once in a climb, we declared min fuel and asked for vectors around a storm north of the field and then to proceed direct to Offutt. Passing 8,000 feet MSL we asked about field conditions at Will Rogers World Airport, the Oklahoma City airport 10 miles west; no windshear reported. We recovered at Will Rogers with an N2 engine exceedance and our seat cushions secured tightly in our backsides. Long into crew day, we elected to call it a night.

In hindsight, we should not have made the second approach at Tinker. Our min fuel pitch limit of 8 degrees nose up is only half of the 16-degree target pitch for windshear recovery. Sixteen degrees nose up pitch uncovers the forward fuel tank boost pumps, a very undesirable condition while demanding rated thrust during a go-around. Had I asked for a few turns in holding prior to descent, we could have discussed these considerations and then reviewed the procedural change of holding our configuration in the event of a windshear go-around. In a sense we were lucky to be so low on fuel; windshear experiments in the simulator at heavier gross weights aren’t as forgiving. With 27,000 pounds of fuel, we weighed a relatively light 209,000 pounds that night. Had we been at max landing weight of 250,000 pounds, we might have been pressing our luck on the go-around. Luck of the Irish is nice to have, but preparation for the approaches would have been better.