(EDITOR'S NOTE: The new F-105F Thunderchief is one of the most awesome weapons in the arsenal of the Air Force. A two-seater version of the F-105D fighter-bomber, it can fly in any weather at about twice the speed of sound and deliver a nuclear payload. In Germany recently, Francis (Red) Grandy, photo chief of the European Stars and Stripes, became the first newspaperman to ride a Thunderchief. Here is Grandy's story.)

WE FLEW THE TACTICAL aircraft the Kremlin fears the most in a vivid demonstration of the awesome power of a modern U.S. Air Force weapons system.

Riding the sonic boom behind the educated nose of the Republic F-105F Thunderchief we got a back-seat view of the strike capability of a remarkable aircraft once described as equipped to do "everything but salute."

The sleek, two-seat version of the F-105D for the first time made it possible for observers to witness in action a fighter-bomber that can fly in any weather, at speeds up to twice that of sound and automatically deliver nuclear weapons or a conventional payload greater than that carried by the average World War II heavy bomber.

Flown by veteran Republic Aviation test pilot Harry Evans, our mission was one of 40 staged by the Air Force to demonstrate the Thunderchief's. capabilities to U.S., British, German, Canadian and French military personnel.

The F-105F's big J75 jet engine rocketed us off the runway at Ramstein AB, Germany, like an express elevator. While we were climbing, Evans triggered to life the electronic computers stacked in the belly of the Chief.

Automatically the Thunderchief's navigation and flight control systems took over, guiding us to 10,000 feet and swinging southeast to our destination, demonstrating how this aircraft can operate itself in blind flying conditions.

The earth disappeared under a layer of clouds. Over: the intercom, Evans told me he could fold his arms while our electonic copilot took us to Lake Ammer near Munich.

In the black box compartment below us, a doppler navigation system was in command, digesting information supplied by the radar in the nose cone and issuing electronic orders to the autopilot.

Winds, drift angles, speed all were computed by the black boxes and continually interpreted on the instrument panel in terms of where we were and how far we had left to go. If desired, Evans could have called and checked our position.

DESCENDING over Lake Ammer, the cloud-covered Alps were clearly profiled on the radar screens. Evans demonstrated the terrain avoidance system, which warned us that if we continued on our course we would make the biggest sitzmark ever seen on the ski slopes of Germany's highest mountain, the Zugspitze.

Banking, we broke into a cloudless area and I asked if we could make a roll to shoot some photographs. Before we would discuss it, the earth moved out from under me, swung dizzily over my head and back below me again, and Evans asked: "How's that?"

I managed, "Well, ah ..." before earth and sky rolled crazily again, only slower. Just as I recovered, we did a tight roll and I was sorry I had brought up the subject.

The 18-ton Thunderchief maneuvered without a vibration or flutter.

Our flight plan included a simulated bomb toss, and for the benefit of the cameras, Evans performed a loop, approximating the maneuver that can be employed to lob a bomb onto a target.

I relaxed while Evans pulled up the Chief's nose. A gravitational pull four times my weight pressed me into the seat and everything grew dark as I fought blacking out.

Vision cleared again as we rode over the top of the loop and dived straight down at the lake.

Pulling up, Evans started a supersonic dash. An exhilarating forward thrust signaled that the powerful afterburner had been ignited, and the airspeed indicator began spinning madly.

While I anticipated some spectacular sensation, Evans calmly commented: "We're supersonic." The Thunderchief had already blasted a sonic boom up into space.

Had our flight been in anger, the F-105 could have delivered any of 4,000 different combinations of nuclear or conventional high explosive or napalm fire bombs, rockets or missiles.

A total of 6½ tons of weapons, more than twice the payload of a B-17 Flying Fortress of World War II, could have been carried for the attack.

Our mission could have been to support ground troops, or to strike targets behind enemy lines. For our own defense we could have used the Chief's electrically operated gatling-type 20mm cannon, capable of firing 6,000 rounds a minute, or the lethal Sidewinder, a heat-seeking air-to-air missile.

To make sure the payload is pinpointed on a target, a fire control system linked to the navigation and flight controls automatically directs the aircraft to its objective, releases its weapons and sets it on its home course.

Our doppler banked us northwest again, its counter clicking-off the miles left to Ramstein. The reading dropped until it registered zero smack over the base runway.

It was our electronic copilot's way of telling us we were home. As we made our approach, the earth seemed pale after 80 minutes of riding this manned missile through the pilot's world above.