Operation ENDSWEEP

a short summary by
LtCol John Van Nortwick  USMC Retired

1973

In January, HMA-369's very unique and successful "hunter-killer" operations were terminated to prepare for the upcoming Operation Endsweep.

HMH-463 (CH-53D's) with Dets from HMM-164 (CH-46D's) and HML-167 (UH-1E's) attached; and HMM-165 (a composite squadron with a mix of CH-53D's, CH-46D's and UH-1E's) joined TF 78, together with the Navy's HM-12 (RH-53A's).  Endsweep was tasked with the clearance of US-laid sea mines from Haiphong Harbor and its approaches in accordance with the then on-going Paris Peace Accords.  The operation was unique in many ways and required that the Marines assigned utilize high levels of ingenuity, flexibility, and political awareness.  The key words were "High Theatre", as the operation was based on the statistical theory that a given number of mine sweeps in a given geographical area would produce a 99.9% assurance that no more live mines were present.  The detonation of actual mines was minimal, but when that occured, it was most impressive.  The hazards to the aircraft and aircrews lay in the flight envelope required to accomplish the mission.  This envelope, summarized as 35 knots airspeed, 35 feet AGL, ball way out, high gross weights, and downwind in many cases required very high power settings and caused unusual stress on airframes and flight control systems.  The loss of 3 A/C (2 Marine, 1 Navy) during ENDSWEEP was attributed to material failure in each case.  Fortunately, no lives were lost.  Initially, activities were limited to the installation of minesweeping kits (a streaming winch, a tow kit, flight control system modifications, a precise navigation system based on Loran, rearview mirrors, and 2 internal fuel cells) and AMCM aircrew training with the Magnetic Orange Pipe (MOP) at NAS Cubi Point.  Even these activities were curtailed for security reasons.  Word was that the bars in Olongapo were full of NVA "spies" that reported all TF78 activity to Hanoi.  Although, probably not every activity was reported.  On 28 February, 1973, after modifying all 15 of their 53's, conducting AMCM training for all of their own crews plus those of HMM-165 and HMH-462, who were being held in reserve, and enduring numerous green side/brown side out drills caused by the political environment, 463 and 165 deployed to the Grand Norway Island area outside of Haiphong Harbor with the rest of TF78.

Again, political considerations at higher levels delayed the start of ENDSWEEP until 12 March.  At that time, Det D of HMH-463, now aboard USS Cleveland commenced operations in the lach Huyen area of Haiphong harbor.  In order to maintain one A/C continuously sweeping, it was necessary to launch 6 three hour sorties per day.  The Det provided three of these sorties while the squadron aboard Inchon provided the remainder.  At the same time, CH-53D's of HMM-165 provided support to HM-12 using the Mark 105 Seaborne Equipment Platform, a hydrofoil sled.  A typical minesweep sortie consisted of towing the MOP or Mark 105 from the stern gate of the LPD to the assigned minefield, sweeping under the control of a nearby Navy minesweeper (MSO) for two hours, and a thirty minute return to the LPD.

During the next four months, 463 and 165 learned new AMCM techniques and equipment on the job, cleared many areas near Haiphong and other ports, rotated back and forth to/from Cubi for maintenance, and endured the continuing political delays.  By July, when ENDSWEEP was concluded, HMH-463, HMM-165, and HM-12 towed a variety of mine clearnce devices over 27,000 miles, more than the circumfrance of the earth, and logged over 2,000 hours of tow time.

On behalf of the Airborne Mine Countermeasures (AMCM) Reunion Association, I would like to thank LtCol John Van Nortwick for his article on ENDSWEEP and the above summary that he submitted.  I'm sure the Colonel would love to hear from fellow AMCM people, especially those that took part in Operation ENDSWEEP.  

The Colonel can be reached by e-mail at raceman@whc.net

Last revised on 25 December, 1999 © Airborne Mine Countermeasures Association, Virginia Beach, Virginia. Webmaster - Barry Marple Virginia Beach, VA. Domain name property of Barry Marple. All rights reserved.