Tuesday, August 17, 2010

Sonic Booms over Seattle

Recently there were sonic booms over the Puget Sound region.

These sonic booms were set off by a pair of F-15 fighter jets that were scrambled to intercept a small seaplane that had violated a Temporary Flight Restriction (TFR) around the President of the United States. He was in town fund raising for our embattled Senator, Patty Murray.

There is crazy amount of disinformation around events like these. As a certified pilot with 15 years of experience with the system, I’d like to address some of these items.


  1. Sonic Booms occur when an object travels faster than the speed of sound, and is produced continuously along it the path it travels. In the article by ABC news it is reported “The sonic booms created by the fighter jet engines...” The booms are NOT caused by the engine, unless you consider the engine is what pushes the entire airframe through the air.
  2. The speed of sound varies based on the density of the media the sound waves are traveling in. Since air gets less dense at higher altitudes, the speed of sound is lower as you go up. Roughly it is around 770 mph down at sea level.
  3. There are speed limits in the sky over the continental United States. Generally an aircraft may not exceed 250 kts (287 mph) below 10,000 feet. Above 10,000 ft, an aircraft may not exceed the speed of sound – without a waiver. The military has a waiver.
  4. At high altitude, the F-15 will go about 2.5 times the speed of sound or around 1,600 mph, at low altitude it only goes 1.2 times or around 900 mph. If the plane is loaded with weapons such as external bombs or fuel tanks, the airspeed is further reduced due to drag.
  5. The F-15s came from Portland because those are the nearest armed fighters. All of the fighter wings that were based nearer have been removed. There are transport jets (C-5, C-141, and C-17) and heavy helicopters (CH-47) in Tacoma, Electronic Jammers (EA-6B, EA-18G, P-3) and on Whidbey Island, and Bombers (B-52H) in Spokane. But the nearest armed fighters are in Portland.
  6. Restricted areas

  7. How big is the TFR? The restricted space is 30 miles in radius. Imagine a circle that extends from south of Tacoma to Everett and from the east slopes of the Olympic Mountains to the west slopes of the Cascades. Aircraft may only be operated in that ring if they are working with Air Traffic Control (ATC) and entering or leaving the area.
  8. There is also an inner ring that is only ten miles in radius. Only law enforcement aircraft are allowed in there.
  9. The President ALWAYS has a 30 mile ring around him when he is on the ground. It is slightly smaller when he is in flight.
  10. Does the President need all that space? I don’t know. For a typical small airplane that only goes about 120, it is a 15 minute buffer from incursion to center of the TFR. But for a faster plane like an airliner, it could be a quarter of that.
  11. Pilots talking to Air Traffic Control and Flight Plans

  12. Since flight on Visual Flight Rules (VFR) flights require NO prior authorization from the government, there is NO ATC talking to the pilot to stop them. Quite literally, if I had enough fuel, I could take off from Copalis beach on the pacific coast in Washington state, and fly all the way to Homestead General Airport in southern Florida, and NEVER talk to ATC.
  13. The purpose of a Flight Plan on a VFR flight is to help search and rescue know where to look for the wreckage. Really. If I file a VFR flight plan, after taking off, I call a special frequency for that area, and ask them to open my flight plan. Upon arriving at the other end, I call another special frequency to close it. If I fail to close it, they assume that I did not arrive at my destination. And they will call out the search and rescue teams that will then search along my intended course looking for the plane. Remember when Steve Fossett disappeared? No flight plan. They are not required. It took a year to find the wreckage and that was by a hiker on accident.
  14. The pilot should have checked for a Notice to Airman (or NOTAM) prior to the flight. Since the President is always surrounded by a TFR, and it has been known for days that he would be in town, and the pilot is REQUIRED to check for NOTAMs prior to his flight, he should have known.