Thanks Mike - very interesting.
Regards,

On 2 May 2007 12:11:15 -0700, Mike Weeks wrote:

On Apr 27, 9:05?am, Charlie Wolf wrote:
Anybody heard anything yet?
y best guess (and ONLY a guess) is bird
ingestion....

Anything would be appreciated...

The following might be of some interest. It come from


Blue Angel # 6 crashed about 4:00 p.m. on April 21, three miles from
Marine Corps Air Station Beaufort in South Carolina.

The F/A18 clipped the top of a tree during a formation rejoin behind
the crowd, in preparation for the team's grand finale flypast for a
pitch and break into the circuit for landing.

Understanding why these spectacular accidents happen increases the
aerodynamic body of knowledge for accident investigators in the
commercial aviation arena.

The aircraft wreckage was scattered along a rural roadway, hitting a
vehicle and several homes. Eight people on the ground were injured and
the pilot died. This was the 26th death in the aerobatic team's
history and the third fatal Blue Angels crash in 10 years.

In 1999, two pilots of the Blue Angels were killed when an F/A-18
crashed into a stand of pine trees in Georgia, as the team
practiced for a show. The rejoin join-up comes after the downward bomb-
burst known as the fleur-de-lis (or Delta Vertical Break) scatters
the six team-members to the four points of the compass.

Conjecture about the cause of these crashes has centered on the fact
that the team doesn't wear lower body G suits because the sudden
inflation of the suit under G onset can affect the delicate stick-grip
required for close formation flying. The inference is, that G-LOC (or
G induced loss of consciousness) may have been to blame.

Others have hypothesized about a birdstrike penetrating the canopy and
disabling the pilot.

However, there is another possible explanation, based on eyewitness
accounts of the aircraft's final maneuvering and a snatch of video
footage.

During the low-level rejoin, the classic threat is that of the
concentration and focused gaze of the rejoining pilot on the low
( inside ) side of the leader's turn towards him being upward. ( i.e.,
he is looking up skywards at the lead aircraft and also taking spacing
on the aircraft that he is supposed to follow in the rejoin ).

For geographic positioning, if the leader banks slightly further
toward the rejoining # 6 this can have a much magnified and
disproportionate effect on the team-member rejoining from well down on
the "low side."

It can cause for the rejoining team-member an unnoticed and
inadvertent significant height loss.

This consequence is caused by the distant rejoining team-member
rolling in concert with the leader's roll to a higher bank angle, to
maintain his correct extended echelon rejoin "line" of relativity
( and to keep visual contact.)

This is a well-known cause of accidents in military rejoins,
particularly at night or over water, where [ the low man's ]
inadequate peripheral vision of the proximity of terrain/water can
fail the " low-man " formation rejoiner, simply because of where he
is looking.

The dynamics of the Blue Angels crash are difficult to visualize in
four dimensions.

However, # 6, joining in turn as the last rejoiner, had to resolve
his early rejoin geometry and go from high 8:30 ( relative to Lead )
with a large heading differential to low on the inside of the leader's
left turn ( as the formation re-formed up behind the crowd at 500 feet
AGL.)

In the video of the mishap, the aircraft is seen in a steep left bank
with a high descent rate.

He gets through about 90 degrees of turn, rolling left and descending,
still looking towards Lead for his echelon rejoin line and to be co-
planar with Lead's bank-angle.

He is about 1,500 feet behind when he vanishes into the treetops.

To visualize an "echelon rejoin line", think of a line between the
leader's eyes and his own port wingtip, and extend it.

That projected line changes both as Lead turns ( laterally) and
whenever he rolls ( vertically.)

Lead can therefore unintentionally influence a large height change on
a distant rejoiner looking to straddle that line, simply by changing
his bank angle.

Why does the rejoiner need that line?

Rejoin geometry says that for a brisk but controlled rejoin, he must
rejoin along that echelon line ( or just below it ) or risk latterly
losing sight of the leader ( or the whole formation ) below his RH
canopy sill, and that would constitute a severe collision hazard.

The dilemma is that his concentration and focus must necessarily be on
the formation ( to his right and above) and the required geometry
of his rejoin. And so he can fatally forget momentarily about the
ground on his lower left-hand side.

A moment is all that it takes.

Overcooked rejoins have always been one of the greater formation
flying threats, particularly at low-level and with the added pressure
of time when performing in front of a crowd.

Joe Farrell, who had a plane on display at Saturday's air show,
comments that # 6 largely appeared in control.

" It looked like it was in absolute control all the way into the
ground," Farrell says. " We watched the guys try to reform. He made
the turn and slid right into the ground."

Saturday's airshow was the seventh display from the commencement of
the team's flight season, which began last month.

The F/A18's flight recorder was found in a pond next to the crash
site. Military investigators say it is in good shape, and it has been
sent away for analysis.

The Navy's Blue Angels are stationed in Pensacola and scheduled to fly
in another 66 air shows this year.