Narrative:

My wife (who is also a commercial pilot with instrument rating) and I were on an instrument currency flight in a cessna 172. I was PIC and was flying the airplane under the hood. My wife was acting as safety pilot and there was another rated pilot in the rear seat who was assisting with safety monitoring. We had just completed an NDB approach to the tacoma narrows airport and had requested a PAR approach at gray army air field from the seattle approach controller. Seattle approach gave us a vector of 160 degrees and 2000 ft and handed us off to the gray final approach controller. After establishing communication, the gray final approach controller advised us that we were on an 8 mi final, gave us a 5 degree heading adjustment and cleared us for the PAR, low approach. On approximately a 6-7 mi final, the gray controller called traffic at 2 O'clock. My wife and passenger immediately spotted the traffic which appeared to be below us and proceeding nebound. At this point, because the controller had not indicated otherwise, my wife and passenger concluded that the aircraft would continue northeast across our approach path. My wife stated later that from the confign of the running lights, she thought the aircraft might be a small commuter aircraft inbound to seatac. Our passenger thought it more likely to be a helicopter because of its apparent low altitude. The aircraft did not seem to pose a hazard, but to increase separation, my wife suggested that I reduce approach speed, and I complied, slowing the aircraft to 80 KTS. My wife and passenger followed the aircraft closely as it appeared to cross our approach path, at which time it was deemed no longer a factor. Shortly after, the controller advised us we were on a 4 1/4 mi final, we should expect to execute missed approach at 1 mi, and that the airport lights would be extinguished because our traffic, 12 O'clock and 2 mi was a C-130 executing a 'blackout landing.' my wife and passenger were unable to see the traffic at all, and believe that the C-130 had its running lights extinguished at this time. This call from the gray controller was the first time we were informed of the type of the aircraft, or that any aircraft at all would be ahead of us on the approach. My wife and passenger believe that the aircraft they had been following earlier must have made an abrupt, combat-style turn onto the final approach course ahead of us, but this was not perceptible to them at the time. Almost immediately after the radio call advising us of the presence of a c- 130 ahead (and before we could absorb the import of this information) we encountered moderate turbulence which we all recognized as wake turbulence. I immediately began to execute missed approach procedures, applying full power and beginning to pitch up. After a moment of relatively smooth flight, we encountered severe turbulence and an uncommanded roll to the left which continued to at least 120 degrees despite full, opposite aileron and rudder deflection. My hood had flopped down over my eyes during the initial encounter with the turbulence, but by tilting my head back I could see the attitude indicator. My instinct was to lower the nose to gain airspeed and control authority/authorized, but in fact, because of our near-inverted attitude, this resulted in negative G's and our charts, clipboards and other flight equipment hit the ceiling. At this point the engine quit, although the propeller continued to windmill (I could see this because the negative G's flipped my hood up out of the way). We maintained this attitude for a moment, and then the aircraft began to respond to the control input and we rolled to wings level. Because I had not relaxed all of the forward pressure as we rolled level, we were pitched down 30-40 degrees as we reached wing level. Since our airspeed was still fairly low (under 100 KTS) I was able to recover from the dive easily, at which time the engine came back to life. We then executed missed approach procedures and advised the gray controller that we were terminating the approach because of an encounter with wake turbulence. The controller gave no indication that he was aware of the situation or concerned about our report of wake turbulence. Throughout our engine-out inverted flight maneuver his matter- of-fact instructions continued ('well below glide path, diverging, slightly left of course' etc) and when we advised him of our missed approach he immediately signed us off with a cheery 'contact seattle approach, good day!' our initial encounter with the turbulence was at or above 800 ft MSL, and we completed our recovery at 600 MSL, which at this location, appears to be about 250-300 ft AGL. It is my judgement and that of my wife and passenger that this wake turbulence encounter was very close to being unrecoverable. I believe that my instinct to lower the nose to gain airspeed probably saved us, although not in the way I intended. It appears that it allowed us to maintain controled flight at a reasonable airspeed (by holding the nose 'up') long enough to get out of the vortex and recover. Had I pulled instead of pushed, I believe it would have initiated an inverted dive from which we would not have had sufficient altitude to recover. We believe that this incident could have been avoided if the following procedures had been followed: 1) the controller should have idented the aircraft type and intentions when calling traffic, particularly since we would be following the aircraft on a final approach. The controller never informed us of the aircraft type or that we would be following another aircraft on the approach until it was too late to avoid the wake turbulence. 2) the controller should have applied the required wake turbulence separation criteria for light aircraft. There was no urgency for us to fly the PAR approach at that moment - we would have been happy to hold or comply with vectors for spacing. 3) we are glad that the military provides civilian pilots with the opportunity to experience a precision approach in order to maintain controller proficiency and we hope this policy will continue, but we would suggest that civilian practice approachs to military installations where 'blackout' or other combat practice maneuvers are in progress should be temporarily suspended as a matter of standard procedure. We would request that the information in this report along with our suggestions be forwarded to the appropriate authorities at gray for their consideration. This incident report was prepared by myself, my wife and my passenger within 2 hours of landing. Callback conversation with reporter revealed the following information: reporter states the incident took them so much by surprise because they did not even have time to look for and sight the traffic. Reporter feels the aircraft must have just turned on to final ahead of them when traffic was called by approach controller. In discussing the event after the fact with other pilots, they have wondered what can one do to control the situation when such a wake turbulence encounter is experienced? Is there any training one can do? Reporter was encouraged to communication the experience with gray approach facility and with local FSDO.

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Original NASA ASRS Text

Title: C172 ON PAR APCH TO MIL FIELD ENCOUNTERS WAKE TURB FROM C130.

Narrative: MY WIFE (WHO IS ALSO A COMMERCIAL PLT WITH INST RATING) AND I WERE ON AN INST CURRENCY FLT IN A CESSNA 172. I WAS PIC AND WAS FLYING THE AIRPLANE UNDER THE HOOD. MY WIFE WAS ACTING AS SAFETY PLT AND THERE WAS ANOTHER RATED PLT IN THE REAR SEAT WHO WAS ASSISTING WITH SAFETY MONITORING. WE HAD JUST COMPLETED AN NDB APCH TO THE TACOMA NARROWS ARPT AND HAD REQUESTED A PAR APCH AT GRAY ARMY AIR FIELD FROM THE SEATTLE APCH CTLR. SEATTLE APCH GAVE US A VECTOR OF 160 DEGS AND 2000 FT AND HANDED US OFF TO THE GRAY FINAL APCH CTLR. AFTER ESTABLISHING COM, THE GRAY FINAL APCH CTLR ADVISED US THAT WE WERE ON AN 8 MI FINAL, GAVE US A 5 DEG HDG ADJUSTMENT AND CLRED US FOR THE PAR, LOW APCH. ON APPROX A 6-7 MI FINAL, THE GRAY CTLR CALLED TFC AT 2 O'CLOCK. MY WIFE AND PAX IMMEDIATELY SPOTTED THE TFC WHICH APPEARED TO BE BELOW US AND PROCEEDING NEBOUND. AT THIS POINT, BECAUSE THE CTLR HAD NOT INDICATED OTHERWISE, MY WIFE AND PAX CONCLUDED THAT THE ACFT WOULD CONTINUE NE ACROSS OUR APCH PATH. MY WIFE STATED LATER THAT FROM THE CONFIGN OF THE RUNNING LIGHTS, SHE THOUGHT THE ACFT MIGHT BE A SMALL COMMUTER ACFT INBOUND TO SEATAC. OUR PAX THOUGHT IT MORE LIKELY TO BE A HELI BECAUSE OF ITS APPARENT LOW ALT. THE ACFT DID NOT SEEM TO POSE A HAZARD, BUT TO INCREASE SEPARATION, MY WIFE SUGGESTED THAT I REDUCE APCH SPD, AND I COMPLIED, SLOWING THE ACFT TO 80 KTS. MY WIFE AND PAX FOLLOWED THE ACFT CLOSELY AS IT APPEARED TO CROSS OUR APCH PATH, AT WHICH TIME IT WAS DEEMED NO LONGER A FACTOR. SHORTLY AFTER, THE CTLR ADVISED US WE WERE ON A 4 1/4 MI FINAL, WE SHOULD EXPECT TO EXECUTE MISSED APCH AT 1 MI, AND THAT THE ARPT LIGHTS WOULD BE EXTINGUISHED BECAUSE OUR TFC, 12 O'CLOCK AND 2 MI WAS A C-130 EXECUTING A 'BLACKOUT LNDG.' MY WIFE AND PAX WERE UNABLE TO SEE THE TFC AT ALL, AND BELIEVE THAT THE C-130 HAD ITS RUNNING LIGHTS EXTINGUISHED AT THIS TIME. THIS CALL FROM THE GRAY CTLR WAS THE FIRST TIME WE WERE INFORMED OF THE TYPE OF THE ACFT, OR THAT ANY ACFT AT ALL WOULD BE AHEAD OF US ON THE APCH. MY WIFE AND PAX BELIEVE THAT THE ACFT THEY HAD BEEN FOLLOWING EARLIER MUST HAVE MADE AN ABRUPT, COMBAT-STYLE TURN ONTO THE FINAL APCH COURSE AHEAD OF US, BUT THIS WAS NOT PERCEPTIBLE TO THEM AT THE TIME. ALMOST IMMEDIATELY AFTER THE RADIO CALL ADVISING US OF THE PRESENCE OF A C- 130 AHEAD (AND BEFORE WE COULD ABSORB THE IMPORT OF THIS INFO) WE ENCOUNTERED MODERATE TURB WHICH WE ALL RECOGNIZED AS WAKE TURB. I IMMEDIATELY BEGAN TO EXECUTE MISSED APCH PROCS, APPLYING FULL PWR AND BEGINNING TO PITCH UP. AFTER A MOMENT OF RELATIVELY SMOOTH FLT, WE ENCOUNTERED SEVERE TURB AND AN UNCOMMANDED ROLL TO THE L WHICH CONTINUED TO AT LEAST 120 DEGS DESPITE FULL, OPPOSITE AILERON AND RUDDER DEFLECTION. MY HOOD HAD FLOPPED DOWN OVER MY EYES DURING THE INITIAL ENCOUNTER WITH THE TURB, BUT BY TILTING MY HEAD BACK I COULD SEE THE ATTITUDE INDICATOR. MY INSTINCT WAS TO LOWER THE NOSE TO GAIN AIRSPD AND CTL AUTH, BUT IN FACT, BECAUSE OF OUR NEAR-INVERTED ATTITUDE, THIS RESULTED IN NEGATIVE G'S AND OUR CHARTS, CLIPBOARDS AND OTHER FLT EQUIP HIT THE CEILING. AT THIS POINT THE ENG QUIT, ALTHOUGH THE PROP CONTINUED TO WINDMILL (I COULD SEE THIS BECAUSE THE NEGATIVE G'S FLIPPED MY HOOD UP OUT OF THE WAY). WE MAINTAINED THIS ATTITUDE FOR A MOMENT, AND THEN THE ACFT BEGAN TO RESPOND TO THE CTL INPUT AND WE ROLLED TO WINGS LEVEL. BECAUSE I HAD NOT RELAXED ALL OF THE FORWARD PRESSURE AS WE ROLLED LEVEL, WE WERE PITCHED DOWN 30-40 DEGS AS WE REACHED WING LEVEL. SINCE OUR AIRSPD WAS STILL FAIRLY LOW (UNDER 100 KTS) I WAS ABLE TO RECOVER FROM THE DIVE EASILY, AT WHICH TIME THE ENG CAME BACK TO LIFE. WE THEN EXECUTED MISSED APCH PROCS AND ADVISED THE GRAY CTLR THAT WE WERE TERMINATING THE APCH BECAUSE OF AN ENCOUNTER WITH WAKE TURB. THE CTLR GAVE NO INDICATION THAT HE WAS AWARE OF THE SIT OR CONCERNED ABOUT OUR RPT OF WAKE TURB. THROUGHOUT OUR ENG-OUT INVERTED FLT MANEUVER HIS MATTER- OF-FACT INSTRUCTIONS CONTINUED ('WELL BELOW GLIDE PATH, DIVERGING, SLIGHTLY L OF COURSE' ETC) AND WHEN WE ADVISED HIM OF OUR MISSED APCH HE IMMEDIATELY SIGNED US OFF WITH A CHEERY 'CONTACT SEATTLE APCH, GOOD DAY!' OUR INITIAL ENCOUNTER WITH THE TURB WAS AT OR ABOVE 800 FT MSL, AND WE COMPLETED OUR RECOVERY AT 600 MSL, WHICH AT THIS LOCATION, APPEARS TO BE ABOUT 250-300 FT AGL. IT IS MY JUDGEMENT AND THAT OF MY WIFE AND PAX THAT THIS WAKE TURB ENCOUNTER WAS VERY CLOSE TO BEING UNRECOVERABLE. I BELIEVE THAT MY INSTINCT TO LOWER THE NOSE TO GAIN AIRSPD PROBABLY SAVED US, ALTHOUGH NOT IN THE WAY I INTENDED. IT APPEARS THAT IT ALLOWED US TO MAINTAIN CTLED FLT AT A REASONABLE AIRSPD (BY HOLDING THE NOSE 'UP') LONG ENOUGH TO GET OUT OF THE VORTEX AND RECOVER. HAD I PULLED INSTEAD OF PUSHED, I BELIEVE IT WOULD HAVE INITIATED AN INVERTED DIVE FROM WHICH WE WOULD NOT HAVE HAD SUFFICIENT ALT TO RECOVER. WE BELIEVE THAT THIS INCIDENT COULD HAVE BEEN AVOIDED IF THE FOLLOWING PROCS HAD BEEN FOLLOWED: 1) THE CTLR SHOULD HAVE IDENTED THE ACFT TYPE AND INTENTIONS WHEN CALLING TFC, PARTICULARLY SINCE WE WOULD BE FOLLOWING THE ACFT ON A FINAL APCH. THE CTLR NEVER INFORMED US OF THE ACFT TYPE OR THAT WE WOULD BE FOLLOWING ANOTHER ACFT ON THE APCH UNTIL IT WAS TOO LATE TO AVOID THE WAKE TURB. 2) THE CTLR SHOULD HAVE APPLIED THE REQUIRED WAKE TURB SEPARATION CRITERIA FOR LIGHT ACFT. THERE WAS NO URGENCY FOR US TO FLY THE PAR APCH AT THAT MOMENT - WE WOULD HAVE BEEN HAPPY TO HOLD OR COMPLY WITH VECTORS FOR SPACING. 3) WE ARE GLAD THAT THE MIL PROVIDES CIVILIAN PLTS WITH THE OPPORTUNITY TO EXPERIENCE A PRECISION APCH IN ORDER TO MAINTAIN CTLR PROFICIENCY AND WE HOPE THIS POLICY WILL CONTINUE, BUT WE WOULD SUGGEST THAT CIVILIAN PRACTICE APCHS TO MIL INSTALLATIONS WHERE 'BLACKOUT' OR OTHER COMBAT PRACTICE MANEUVERS ARE IN PROGRESS SHOULD BE TEMPORARILY SUSPENDED AS A MATTER OF STANDARD PROC. WE WOULD REQUEST THAT THE INFO IN THIS RPT ALONG WITH OUR SUGGESTIONS BE FORWARDED TO THE APPROPRIATE AUTHORITIES AT GRAY FOR THEIR CONSIDERATION. THIS INCIDENT RPT WAS PREPARED BY MYSELF, MY WIFE AND MY PAX WITHIN 2 HRS OF LNDG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE INCIDENT TOOK THEM SO MUCH BY SURPRISE BECAUSE THEY DID NOT EVEN HAVE TIME TO LOOK FOR AND SIGHT THE TFC. RPTR FEELS THE ACFT MUST HAVE JUST TURNED ON TO FINAL AHEAD OF THEM WHEN TFC WAS CALLED BY APCH CTLR. IN DISCUSSING THE EVENT AFTER THE FACT WITH OTHER PLTS, THEY HAVE WONDERED WHAT CAN ONE DO TO CTL THE SIT WHEN SUCH A WAKE TURB ENCOUNTER IS EXPERIENCED? IS THERE ANY TRAINING ONE CAN DO? RPTR WAS ENCOURAGED TO COM THE EXPERIENCE WITH GRAY APCH FACILITY AND WITH LCL FSDO.

Data retrieved from NASA's ASRS site as of July 2007 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.