“Kind of like shooting a musket ball out of the air with a slingshot.”
See below analysis from which could apply to GPS targeting of large jet engine on the runway or on a predictable ILS landing approach:
If any two engines on a large multi-engine jet can be disabled in the RKZ by a terrorist attack, the aircraft will not be able to gain enough altitude to return to the airport and will almost certainly crash. The availability of inexpensive, GPS-guided autonomous model aircraft and helicopters (drones and UAVs) that are capable of precisely targeting the runway path of each jet engine in the RKZ makes terrorist attacks increasingly probable.
How big a target for terrorists is the intake turbofan of a Boeing 747 jet engine coming down the runway in the RKZ?
The intake fan diameter of the GE CF6-80C2 turbofan used on Air Force One or a 747-400 is 93 inches (2.36 m) or nearly 8 feet wide (7 ft 9 in).
Are the GPS autopilot systems available for model aircraft and helicopters accurate enough in latitude, longitude and altitude to hit an 8 foot wide target, such as a 747 engine coming down a runway?
The latest drone, UAV, model aircraft and model helicopter GPS autopilot systems are designed to enable autonomous flight and incorporate location accuracy enhancement technologies called DGPS and WAAS. These GPS enhancements enable a location accuracy radius within the radius of a 747 engine intake ( 1/2 of 2.36 meter diameter = 1.18 meters, or 1/2 of 93 inch diameter = 3 ft 8.5 inches).
DGPS location accuracy according to Wikipedia:
“Differential Global Positioning System (DGPS) is an enhancement to Global Positioning System that provides improved location accuracy, from the 15-meter nominal GPS accuracy to about 10 cm in case of the best implementations.”
WAAS location accuracy according to Wikipedia:
“Actual performance measurements of the system at specific locations have shown it typically provides better than 1.0 metre (3 ft 3 in) laterally and 1.5 metres (4 ft 11 in) vertically throughout most of the contiguous United States and large parts of Canada and Alaska.”
What happens if GPS autopilot systems are jammed or the link to a base station gets dropped during a drone attack in the RKZ?
Inertial navigation systems (INS) can take over from the last confirmed GPS coordinates. INS compoments are now available for model aircraft autopilot systems either incorporated into the autopilot system or interfaced to the autopilot system.
While you might pick a spot to place a drone, what you cannot do is pick a spot a plane will be at. The plane cannot re-read and factor out the error, nor does it need to. It just shows the pilot where in the sky the plane is at 4-500 miles an hour and the pilot and autopilot steers the plane to an accuracy that is suitable. At 450 miles per hour, you travel 10 feet in .00017667 seconds. An aircraft GPS keeps the plane in a straight line down a lane that is as wide as a a 250 lane highway. Anywhere in that highway is in your lane. While most pilots would generally tend to drift to the middle of the lane, an 8 foot intake compared to a 229 foot wingspan in a lane that is 23 planes wide is beyond luck.
Just in the horizontal plane, assuming an intake 16 foot wide you have over 600 engines wide staying in the lane!
Adding in a horizontal error of 200 foot vertical drift you are staring at a 30,000 to 1 chance of a hit.
Hitting one engine does not crash the plane, to do that you need to hit two engines.
To put this in perspective:
Chance that Earth will experience a catastrophic collision with an asteroid in the next 100 years: 1 in 5,000
Chance of dying in such a collision: 1 in 20,000
Lightning Strike Probabilities
1. ASSUME -
4 CG flashes/km2/yr/average
House is 10 X 20 m2 = 200 m2
Direct strike to house when lightning hits within 10 m
Predicted strike (1200 X4)/1 000 000 =
4.8 X 10 -3 or once ea. 200 years
Therefore - 1 out of 200 house will be struck per year.
2. ASSUME -
USA population = 280,000,000
1000 lightning victims/year/average
Odds = 1 : 280,000 of being struck by lightning
So if we are going to freak out, lets freak out about being hit by a asteroid, cause that will kill you and blowing out one engine won't. And your odds of being killed by lightning is 3000 times greater than taking out two engines.
900,000,000/280,000 =3,214What happens if GPS autopilot systems are jammed or the link to a base station gets dropped during a drone attack in the RKZ?
Then the plane drifts from the intended path and your odd of sucess begins to go down equal to your drift rate. In real life, nothing changes because you are picking a hit spot at random, there is a 50/50 chance it will drift into your lotto number as drift away.
Can we please put this to rest now?