How do I figure out the altitude of an airplane in flight?

Question

I live one street away from a regional airport and small jets take off over my house every day. I've always been a little nervous about this as most small jet crashes are on takeoff, not on landing. The airport has altitude restrictions on takeoff, but I'm wondering if the pilots are adhering to those policies as they seem a lot lower to me. I was trying to figure out how I can tell how high they are when they pass over my house but can't find anything on the web or on here to help me figure it out. Can anyone help me with this?

Answer 1

Several ways:
i.) estimate altitude given rate of climb
ii.) estimate using trigonometry calculations
iii.) mode C transponders
iv.) go for a ride

Before exploring any of the above, you should understand that pilots generally want to get as high as they can as fast as possible. Among the many reasons is one that you touched on -- safety.

A pilot does not have options if the engine fails when the airplane is low and slow -- shortly after takeoff. Gaining altitude gives the pilot options if there is an engine failure. The most desirable option is to be high enough to be able to glide back to the runway and land without power -- "dead stick" landing. Pilots who do not adhere to this simple safety rule tend to die earlier and probably don't bother you any longer.

Communities more often have noise abatement restrictions that prevent certain departure routes or cause pilots to reduce power over those restricted routes. You should verify what the altitude restrictions are and for what the limitations are designed.

Anyway, let's get back to the solutions. First, let's consider estimating altitude given the max rate of climb.

For self preservation, which is consistent with formal training, pilots will prefer to climb out after takeoff at one of two airspeeds -- best rate of climb or best angle of climb. Best rate of climb is the airspeed that will get the pilot to altitude as fast as possible timewise. Best angle of climb will get the airplane to the highest altitude possible in the shortest distance. Best angle of climb is only advised for trying to clear objects. Imagine an airport with a mountaintop 3 miles from the runway. Otherwise for most airport departures, pilots will use best rate of climb airspeed.

Now, to use that information to estimate altitude you will need to know the type of aircraft and the measured time from when the airplane leaves the ground to when it is over your house. Measuring the time should be relatively easy. Knowing the type of aircraft might be difficult for an untrained person.

I would ask a pilot or other airplane enthusiast you might know for help. Most pilots will be able to recognize airplanes the same way most car enthusiasts can recognize car makes and models even from a distance. Note the aircraft type and the measured time from take off to the point over your house. Then look up the specs of the aircraft type to find the best rate of climb. Simple math will give you an estimated answer. For instance, the ever popular Cessna 182 has a max rate of climb of 924 feet per minute per http://skylane.cessna.com/spec_perf.chtml.

Second, using trigonometry you can stand at a point 1,000 feet from your house. When an airplane looks like it is directly over your house you can measure the angle up to the airplane. For the best results I would try using a sextant. (For your needs you can buy a cheap sextant at a maritime store like West Marine.) I would use a point where your view will be perpendicular to the path of the airplane. Otherwise, depth perception will make it difficult to judge when the airplane is over your house. To find the point 1000 feet from your house I would use either a handheld GPS device or simply use Google Earth (earth.google.com) which has a "measure" tool within the free version. Now, 1000 feet is the base of your triangle. The angle you observed is angle A, and assuming the airplane was directly over your house to construct a 90 degree angle, you can find the airplane's altitude as:

altitude = tan(A)*1000
where A is the observed angle in radians.

Third, mode C transponders tell air traffic controllers the altitude of each aircraft. People are familar with the concept of air traffic controllers viewing radar screens with all the aircraft shown as blips. The blips are from the airplane's transponder. Most transponders also have a "mode C" feature which enables the air traffic controller to not only see the location of each aircraft but also the altitude. I don't know what the FAA's practice is regarding recording or dissemination of that information, however, it is available in realtime to the air traffic controller. Note that while the airport is probably owned by the city, the tower facility is solely within the authority of the FAA. Likewise, the airport manager and other employees would be employees of the city while the air traffic controller works for and reports only to the FAA.

Fourth, there is probably a flying club on the field with planes for rent and instructors. Call the club and ask an instructor to take you up for a ride. Explain what you want to do so the instructor knows the departure path you want -- departure over your house. Then, simply look at the altimeter when over your house. To verify that it is typical departure altitude, have a friend on the ground at your house watch for you. Tell your friend that you will wag the wings 4 times when passing your house. The instructor will be happy to wag the wings 4 times when you say so -- he might even let you do it!

I like math and navigation so options 1, 2, and 3 seem like fun. But even for me, option 4 seems like the most fun and probably the most reliable.

Answer 2

That might be interesting
Estimate method
1.Imagine a right triangle and you are at its lower corner and the jet is positioned at the upper corner. If you can spot the jet by looking into a telescope or even a tube and measure the angle (x), the tube makes with the horizontal, and determine the horizontal distance (L) from you and the plane you can compute its altitude. H=L*tan(x)
More precise method
2.You can also build an optical device by employing a parallax principle. See reference (1) . By employing this principal and the one described earlier (the estimate method) you can build a device capable of determining the altitude quite well. Essentially we have two right triangles orthogonal to each other.

Then h = d sin(x) (first triangle)
d = b tan(y) (second triangle)
Or h = b sin(x) tan(y)
h - target’s altitude
x - angle measured as shown in ref (1)
y – angle measured as discussed in method 1
d – distance to target
b – base distance, distance two optical sights as shown in ref (1)

Answer 3

You sound like you are from the Santee, California area. Is the a Gillespie Field near you? Perhaps Santa Barbara?

Answer 4

The airplanes do show you how high you are flying. The pilots always make sure that they are at the right altitude through this.

Answer 5

You must know the make and model of the aircraft in question. Then you can find the exact wingspan and other dimensions. Take a picture of the plane as it flies overhead, From that information you can calculate the ratios of deference and then the altitude.

Answer 6

how about binoculars with a range finder in them ??

Answer 7

try
http://www.flightview.com/TravelTools/
it gives real time info about flights