Masters Theses

Date of Award

12-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Aviation Systems

Major Professor

Mr. R. B. Richards

Committee Members

Mr. R. J. Ranaudo, Dr. U. P. Solies

Abstract

The United States Naval Test Pilot School (USNTPS) experienced a helicopter mishap on 05 August 2001. The USNTPS Commanding Officer believed that this mishap occurred in large part due to the extremely high workload being placed onto both the school’s students and instructors. As a result of this belief, the USNTPS Commanding Officer ordered his staff to implement the following three orders:

  1. Immediately reduce syllabus exercises by 10%.
  2. Begin to revamp each syllabus in order to reduce the student workload by 25%.
  3. Review syllabus aircraft requirements and recommend one aircraft that can be eliminated from the syllabus inventory without degradation in the school’s ability to accomplish7 its assigned mission.

The first order was completed promptly. The second order was partially completed as a result of reducing the number of exercises in each syllabus, and by restructuring the requirements of each syllabus; however, the 25% student workload was not fully achieved. In order to achieve the desired 25% student workload reduction sought in the second order, the USNTPS Rotary Wing staff proposed that two of the helicopters currently in use during the USNTPS Rotary Wing syllabus, the TH-6B and the OH-58C, be eliminated and replaced by one helicopter that could accomplish all of the missions of the two eliminated helicopters. This proposal would complete the Commanding Officer’s second order by reducing the workload associated with one aircraft and it will also satisfy the last order.

The USNTPS has acted upon the recommendation of the Rotary Wing staff and has decided to replace the TH-6B and the OH-58C, but no definite timetable has been established. A replacement time frame of fiscal year 2006 is desired. The USNTPS has several required characteristics for their replacement helicopter such as: A large flight envelope; a modern, single-piloted helicopter; modern avionics; excellent autorotational characteristics; 2 hours (minimum) endurance with a reserve; and a maximum airspeed of 120 KIAS or greater.

In the author’s opinion, the helicopter that can accomplish both the TH-6B’s and OH-58C’s missions is the Bell 407 helicopter. This statement is based on the author’s knowledge of the USNTPS and on a flight evaluation of the Bell 407 helicopter. There are potentially several other helicopters in the world today that could perform the mission required by the USNTPS; however, this thesis will deal with how the Bell 407 helicopter meets the requirements of the USNTPS Rotary Wing syllabus.

The Bell 407 helicopter is a single piloted, seven-seat, single engine, four-bladed main rotor helicopter manufactured by Bell Helicopter Canada. The maximum normal gross weight is 5,000 pounds and 6,000 pounds with an external load. The airspeed range is 0 to 140 KIAS. The Bell 407 helicopter has dual conventional controls with mechanical linkages. The cyclic, collective, and yaw flight controls are assisted by single stage servo actuators utilizing a single 1,000 pounds per square inch (psi) hydraulic system. The Allison model 250-C47B turboshaft engine delivers 674 shaft horsepower at takeoff power and is controlled via a Full Authority Digital Engine Control (FADEC) system. The main transmission is rated for 674 shaft horsepower at takeoff (5 minute limit) and 630 shaft horsepower at maximum continuous power.

Comparing the Bell 407 helicopter’s characteristics against the required characteristics sought by the USNTPS, it was determined that the Bell 407 helicopter satisfies all of the required characteristics. As a result of this comparison, it is the author’s opinion that the Bell 407 helicopter can successfully replace the TH-6B and the OH-58C helicopters at the USNTPS without any degradation in mission capability.

With this conclusion in mind, it is the author’s opinion that the USNTPS should do the following:

  1. Complete a flight evaluation, to include a full Report of Test Results, of a Bell 407 helicopter by two USNTPS instructors based on the current Rotary Wing syllabus in order to confirm the suitability of the Bell 407 helicopter’s capability to perform the syllabus.
  2. Based on a successful flight evaluation, select the Bell 407 helicopter as the replacement helicopter for the TH-6B and the OH-58C.
  3. Using a Cost/Benefit analysis system, the USNTPS needs to determine which manufacturer supplied and commercially available accessories for the Bell 407 helicopter are required to meet the Rotary Wing syllabus exercise requirements.
  4. Enter into contract negotiations with Bell Helicopter in order to purchase six Bell 407 helicopters with all applicable accessories included for use in the USNTPS Rotary Wing syllabus.

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