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Microburst: It Could Happen to You

By By Keith Cianfrani | April 1, 2016


 

Imagine you are on a return flight to a southern U.S. airport in the summer when you find yourself in unforecasted thunderstorms.

Lightning strikes directly in front of you. You fly into a wall of rain so hard that the sound inside the helicopter is deafening. Visibility drops to zero. You slow the aircraft, and feel its left rear pull down. The tail boom is shaking it like a rag doll.

As your descent continues, the flight director fails. The airspeed indicator on the cockpit’s left side goes to zero. You are in the middle of a thunderstorm microburst. What do you do?

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This is what happened to a helicopter crew attempting to land at an airport in 2012. Due to experience, good coordination and good piloting, this crew lived to tell their story. The following is based on my 2013 interview of the flight’s CFI and review of a video based on information from the on-board flight data monitoring equipment.

Danger Ahead

According to the interview and video, the forecast called for isolated thunder showers beginning at 4 p.m. local time. A 2:55 p.m. update called for winds of 30 to 44 kt with possible hail of 0.5 in within 15 nm of the airfield. At 4:08 p.m., a 5 p.m. weather warning was issued.

The crew knew, based on these warnings, that they had to be back at the airport by 5 p.m. They were on a training flight and planned to return via a copter approach. They did the necessary planning to be back within their 20-min VFR reserve. Going IFR was not in their plans, as they did not expect to encounter instrument meteorological conditions. They looked at their instruments prior to leaving the training area and saw no lightning strikes.

After contacting approach control for clearance to practice a VOR approach, they climbed to 3,000 ft and had more than 10 mi visibility. Approach control never advised that they might be flying into a storm.

They were cleared to descend to 2,000 ft and then for the approach and told to contact the tower when crossing a ground landmark—a nearby, 208-ft-tall water tower.

ATIS was unavailable. Tuning in the tower frequency, the crew heard a controller tell an aircraft that visibility was 10 mi with a 15,000 ft. ceiling.

Shortly before reaching the VOR, a lightning bolt struck in front of the aircraft. The crew encountered heavy rain. Based on the tower’s visibility report, the pilots thought they simply would fly through the rain and be clear on the other side. A second bolt struck. They were in a thunderstorm.

The aircraft descended from 2,000 ft to 1,500 ft, in extremely heavy rain and zero visibility. A routine approach quickly had turned into a very bad situation that was about to get worse.

The crew began their descent from 1,500 ft to the minimum descent altitude (MDA) of 760 ft for the VOR approach. The approach was coupled to indicated airspeed and altitude and dialed in the MDA; the pilots were planning to descend at 70 KIAS, the designated speed for their helicopter.

Since the pilots had a flight plan engaged in the flight management system, the video indicated exactly how far the helicopter was from the missed approach point (MAP) and the exact time it would take to get there. They just couldn’t see. As they approached the MDA, the CFI said, it felt like a hand was pressing down on the aircraft’s left rear. The helicopter did not level off at the MDA, and it did not maintain 70 KIAS. The instructor said it felt like somebody was shaking the aircraft like a rag doll.

The aircraft kept descending. When it reached 650 ft, the flight director failed. The pilots now had to fly manually through the worsening situation.

In a Microburst

The CFI said the volume of air rushing down over the aircraft made airspeed indications on the cockpit’s left side go to zero. He informed the student, but said he still had airspeed indications, albeit erratic, on the right side. The instructor said he would fly the approach.

With the airspeed indication problems, neither pilot realized their aircraft’s stabilator had moved full down. Yet they were still moving across the ground at 70 kt. The stress level in the cockpit reached its highest point, the CFI told me. He said he considered his options and knew he had three major things to contend with: the helicopter’s proximity to the aircraft on the approach in front of it, to the ground and to the water tower to the right of the approach course.

The video based on the flight data monitoring information depicted the pilots’ predicament. The lowest altitude that the aircraft reached was 298 ft agl. Its lowest pitch attitude was 20 deg. All of this was in IMC. At one point, the instructor was pulling 100% torque and was still descending at more than 500 fpm. The crew told the tower that they were 1.3 mi from the missed approach point, which was abeam of the water tower. The CFI later said he remembered briefly seeing the tower out of the chin bubble.

These pilots didn’t have a midair collision. They didn’t crash into the ground, and they didn’t strike the water tower. For the missed approach, they had to climb back up into a storm, with lightning striking around and the aircraft getting low on fuel.

The No. 1 engine’s low fuel light came on. The airfield was only 3 mi away, yet they still couldn’t see it. If No. 2’s low fuel light came on, the instructor said, he would have reconsidered a dive to visual conditions. He decided to remain on the vector. Less than a mile from the runway, they finally broke out of the heavy rain, saw the runway and landed.

On the ground, the pilots complimented each other on their crew coordination and proceeded to shut down the aircraft. The CFI said they were silent during the rest of the shutdown.

This crew did an excellent job dealing with this situation, thus living to tell about it.


Training Points

Encountering a microburst is a situation that no pilot wants to experience. But if you ever do, remember these lessons.

Keep your cool. Maintain good communication. Crew coordination is a must; both pilots must understand it and communicate it. Maintain aircraft control. Stress pitch and power, or attitude and torque.

Ensure that you are proficient in the use of your instruments, and always have a plan and a backup plan. Lastly, let us not forget the training and safety value of having flight data monitoring equipment on board to review the flight.

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