Thunderstorm Avoidance

by Steve on February 19, 2009

The power and energy contained within a convective cell is nothing short of amazing.  If you’ve never had the opportunity to watch a towering cumulonimbus develop, the following time-lapse video will give you a good idea of what it looks like.  At approximately 20 seconds into the clip you will see the “anvil” develop in the upper atmosphere.  This is moisture that has been pushed up into very cold altitudes and has turned into ice.

These storms and aviation do not mix. Pilots are trained to avoid them if at all possible. During my relatively short Navy career in the S-3 Viking I saw plenty of thunderstorms. Oddly enough the carrier was usually directly underneath the only storm around for miles but my worst experience took place before I even made it to a fleet squadron. I was a student Naval Flight Officer in VS-41, the west coast Fleet Replacement Squadron headed on a weekend cross-country training mission to Atlanta from San Diego. Two student NFO’s, an instructor pilot, and an instructor NFO made up the crew. If everything went right we would knock out two syllabus hops on the flight east and another two on the return leg.

The weather briefing focused on convective activity expected over the southeastern US as we approached the Atlanta area later that afternoon. There was a slight chance of thunderstorm activity over the mountains as we departed California but it was forecast at 10% with no embedded cells, fairly standard for AZ/NM in summer. The brief included technique for utilizing the Viking’s surface search radar to scan for thunderstorm cells and discussed limiting its use when not necessary in order to conserve the system’s coolant. We wanted to make sure we had a fully functional radar once we approached the thunderstorm-prone southeastern states. The plan was to radiate at deliberate intervals until clear of clouds just in case there was an embedded cell in our path. Brief, preflight, and departure went as planned. We split the cockpit intercom (ICS) with the front seats on Conference 1 and the back on Conference 2 so that the systems training in the back wouldn’t interfere with the airways navigation training up front.

A couple of quick notes on the Lockheed S-3 Viking for those not familiar with the jet:

  • The Viking’s radar was designed to detect surface contacts at sea.  It is not a weather radar but can be manipulated in ways that will show large storm cells on the scope.  (Also, ATC is not required to assist with weather avoidance.)
  • Viking crews, like all carrier-based jet aviators, all fly with oxygen masks but unlike their fighter brethren, the only time they routinely wear them is during launch and recovery.  Typical S-3 missions involve lower altitudes which keep the pressurized cockpit well below a cabin altitude of 10,000 feet (the threshold where hypoxia becomes a risk).  Plus long missions with a crew of four would deplete the oxygen supply prior to landing.
  • The front and rear seats are separated by the computer consoles located in front of the rear seats.  The distance from the rear stations to the flight stations is approximately 3-4 feet.  Access forward is through an narrow passage between the computer consoles.
  • Crew eject in the S-3 is controlled and initiated by either front seat causing both rear seats to fire simultaneously followed approximately half a second later by both front seats.  The paired ejections ensure that one seat does not trail the other which would likely be fatal to the following occupant or at least result in bad burns.  The crew ejection sequence cannot be initiated by one of the rear seats.  If a rear ejection handle is pulled only that seat fires.

We were cruising along at FL290 (29,000 feet) in and out of harmless clouds, periodically bringing the radar out of standby long enough to confirm a clear path ahead.  The IP and student up front were handling navigation and radios plus discussing syllabus items for the training mission.  The other instructor and I were strapped in the two back seats talking on a separate intercom channel so as not to disturb the training/communications up front.  As we approached Albuquerque, NM we noticed a flight of three B-52’s below us on the exact opposite heading.  We were still in and out of clouds but heard nothing over the Center frequency from the B-52 flight or any other aircraft in the area regarding any bad weather.  We started to see light icing building on the leading edges so the IP called for engine anti-ice and wing de-ice on.  Almost instantaneously after bringing the radar back out of stand-by mode we exited the clouds, saw a hard return on the scope and were staring at the slate grey anvil of a huge thunderhead.  Within seconds we entered rain, then small hail followed by larger hail.  The pilot initiated a right-hand turn away from the threat and instructed his student to let Center know we were deviating for weather.  Hail the size of golf balls was hammering the aircraft and the front canopies spiderwebbed.  The outer layer on the right side delaminated and peeled away.  The turn to the right had exposed the left side of the aircraft to the worst of the damaging hail which caused the large canopy section over the pilot’s seat to explode.  Loose gear, trim panels, and virtually everything attached to the pilot’s survival vest got sucked out of the aircraft.  His oxygen mask and communications cord were also gone.  The rush of loose gear had also disconnected the student’s comm cord.  Trim panels were hanging down mostly blocking the view forward from the rear seats.  Several seconds after the explosive decompression, the pilot lost consciousness and his right arm dangled limply by the center avionics console (this was about all we could see from the back).

We had no way of knowing that the student NFO had taken control of the aircraft and intentionally initiated an emergency decent.  We couldn’t see controlled movement and we couldn’t hear the student who was unaware that his comm cord was disconnected.  We knew we were rapidly decending toward mountainous terrain and could hear Center frantically trying to contact us as they watched our altitude rapidly unwind while on an unassigned heading.  We knew that we were going too fast for a safe ejection but had little choice in the matter.  Through hand signals we agreed to simultaneously eject on the count of three hoping that we would both exit at the same time and not burn the other.  Thankfully at this point the pilot came to and took control of the aircraft.  His student yelled above the wind blast to let him know the speedbrakes were still extended.  In the back we were on the count of “2” when we realized they were alive up front and had control of the jet.

We leveled out at 1200 feet AGL and took stock of the situation.  After passing a mask up front to the pilot and plugging his student back in we ended up working the radios from the back since front seats couldn’t hear over the wind blast.  Using the INS we worked our way toward Albuquerque until Approach picked us up on radar.  The pilot had very limited visibility because the damaged outer layer of his front canopy had not peeled away so the student in the right seat talked him onto the runway while we relayed comms from Approach and Tower from the back.

The damage to the aircraft was extensive.  In addition to the canopies, the nose of the jet and the radar unit behind it were gone plus all leading edges looked as if they had been beaten with sledge hammers.  We were lucky to walk away from that encounter.

Since ABQ shared the field with Kirtland AFB we were taken to medical, checked out, and as with all mishaps, required to pee in a cup.  Once released we headed straight to the O-Club to prove that we were still alive and comtemplate what might remain of our Navy careers.  As we finished dinner and several pitchers we were approached by the flight surgeon who informed us we needed to return to medical and submit new samples since they had screwed up the chain of custody on the originals.  We pointed to the celebratory damage on the table and suggested that they fix their paperwork.

The large canopy panel to the pilot’s left is the one that blew out (frames tail of lead aircraft).



Kath February 19, 2009 at 13:10

Can I ask a question? What would happen — and realizing there’s no finite answer, but you know what I mean — what would happen if you 2 in the back had ejected? Can the plane still — go? Or whatever is over your heads has to get out of the way, of course. Sorry, just wondering.

Steve February 19, 2009 at 18:07

The back seats ejecting would have had no effect on the plane’s ability to fly. The seats in the S-3 were designed to break through the canopies above them (the rear canopies were painted over to reduce glare on the tactical displays). The risk that we faced in this situation was from high speed: ejecting at such speeds tends to result in major injuries from flailing limbs (arms/legs).

Kath February 19, 2009 at 18:53

What about your head??? Yes, I know you had a helmet on, but still — geez. The whole thing is just too scary.

Steve February 19, 2009 at 22:07

I added a picture that will help you out. Behind the pilot’s head is a yellow and black ejection handle. The metal above that is a breaker bar that punches the canopy out as the seat fires up the rails. Your head never hits the canopy. Still scary (and the ride is just starting!)

George September 27, 2009 at 12:31

I was in the Navy from 1972 to 1975, in squadron VS-21. Presently, I teach aerospace and engineering. (VS-41 was next door to us and we all went through training in VS-41 before arriving in VS-21). AMEs worked closely with the Parachute Riggers (PR) and normally shared the same work space, and because of our close relationship to pilot safety, we heard many of the stories. When we began flying the S-3A, it was a brand new aircraft and there were still many bugs to work out of the original design at both the component and systems level. The above story is taking place about 35 years later, and although things do change with time, most of the basics remain the same. I enjoyed reading the story and will be sharing it with my students because it brings us to the real world. However, several issues struck me as I read the piece. One of the most important concepts in flying any aircraft is the concept of “Pilot in Command.” in 1975, we deployed from San Diego, CA to Norfolk, VA to the USS J.F. Kennedy, to make the squadron’s first ever S-3A deployment at sea in the Mediterranean. As I recall, at that time pilots always flew at a minimum, with their clear visor down and their O2 (O2 = Oxygen) mask on. There had been a fatal accident where a bird had gone through the windshield of an A-6 Intruder and the pilot had no visor down and no O2 mask on. We were constantly cleaning and replacing O2 masks. Although our pilots may not have been breathing 100% O2, they were required to wear their mask 100% of the time for O2 control, communications, and emergencies like the one detailed here. I do recall that if either our Skipper (Commanding Officer) or Safety Officer had ever seen flight crew as shown in the photo above, with no mask on, there would have been hell to pay. 🙂 As a further clarification, the Pilot’s (and opposite side) canopy was both on the side and above the pilots head. It started on the side and wrapped around upward to the middle of the overhead. This plastic canopy was heat tempered to make it more brittle and help allow ejection right through it. I had never heard of a situation like that above, but it makes complete sense, and lends credibility to why a pilot should always wear an O2 mask and have some kind of visor down. (If you think this sounds wimpy, search the Internet for information (NTSB Report) concerning the final flight of Golfer Payne Stewart. On 10-25-99, when the Lear Jet he had chartered lost pressurization, the cockpit flight crew had not put on their O2 masks as required by FAA. Everyone on-board was killed and the Lear Jet continued to fly on its own all the way from Central Florida to northern South Dakota where it finally ran out of fuel and crashed). The original S-3A also had windshield delaminating problems, and at one time we had to swap them all out (an incredible job when you consider that each windshield had about 150 screws holding it in, that the laminated windshield was about 3 inches think, and weighed considerably! That was 10 aircraft x 2 windshield sections each, x 150 screws! (Like most jet aircraft, the windshields on the S-3A were heated to promote flexing during bird strikes). As an added tidbit, the S-3A possessed an avionics “growth bay” in the tail section of the aircraft. At that time (1970s) it was considered a big deal to fly to the Denver area and pick up a load of Coors beer. On one flight, after filling the growth bay with a supply of Coors brew, the loaders evidently didn’t secure the external hatch door properly, and during the flight back to San Diego, both the door and brew parted the aircraft. The only remnants of this “actually true sea story” were the slice the door made in the leading edge of the horizontal stabilizer.

Steve September 27, 2009 at 22:23

George if you look carefully at the picture you can barely make out the end of the pilot’s boom mic that’s attached to the left side of his helmet. Not sure about the early days but ’87 on it was NATOPS or SOP that O2 masks were only required for launch/recovery or when behind a tanker. Ironically in the story above the pilot and his student had just been discussing NATOPS requirements for O2 mask usage above certain altitudes when we hit the top of the thunderstorm. Had the pilot been wearing his mask he probably wouldn’t have blacked out but the reality of the Viking’s O2 system was that it didn’t have the capacity to support 4 crew members on oxygen for the duration of an average mission and we definitely would have run short on the cross country.

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