# Do bigger aircraft make a bigger sonic boom?

Jay Carr
• Do bigger aircraft make a bigger sonic boom? Jay Carr

I was watching an episode of MythBusters where they were trying to break glass windows and cups using a sonic boom generated by a F/A-18 Hornet, flown by the Blue Angels. In summary, they were unsuccessful at creating a boom that could shatter the windows, despite a mach speed pass within 200ft of the target building. In the last two passes they even flew straight at the building to focus the boom straight at the house, still no windows were shattered. **

But I've wondered, ever since, if they were unsuccessful because the plane was simply too small. What if the sonic boom had been generated by a B-1 Lancer or perhaps Concorde, which are several times larger than the F/A-18? Logically it seems that since you are displacing more air, the energy wave should have more energy. Then again, the plane isn't going any faster, so perhaps the surface area of the wave would be larger (because of the larger plane) but you wouldn't actually have any more energy at any given point?

Anyone know if a bigger plan than the F/A-18 would have a higher energy sonic boom? And could that cause glass to break?

Bonus point: A mathematical formula showing why, I love those things.

For those curious about what a sonic boom is to begin with, here's a wikipedia article.

**Just to clarify, for those who have seen the episode. A window is broken during the 200ft pass but they say that it only happened because the frame warped, not because the glass itself shattered. Their reasoning is that only that one window broke (out of several windows and glass cups in the area), and it had a pretty cheap frame on it.

• The short version is that yes, larger aircraft create bigger sonic booms, but you still have to be flying very low (less than 100 ft.) and really trying hard in order to damage glass.

A sonic boom is so complicated that you will not find a simple formula to determine the strength. This article describes a modeling tool called PCBoom3 which can be used for sonic boom calculations.

According to several different sites, like this one and this one, the size of the aircraft does affect the intensity:

# Factors Affecting Sonic Boom Intensity

The intensity of sonic booms are affected by:

• Weight, size and shape of the aircraft.
• Altitude
• Attitudeâ€”orientation of the aircraftâ€™s axes relative to the its direction of motion.
• Flight path.
• Atmospheric and weather conditions.

As the size and weight of the aircraft increases, the intensity of the sonic increases. This is because a larger aircraft displaces more air, and a heavier aircraft needs a greater force of lift to sustain flight. Thus creating a louder and stronger sonic boom.

and

# General Factors Associated With Sonic Booms

There are several factors that can influence sonic booms -- weight, size, and shape of the aircraft or vehicle, plus its altitude, attitude and flight path, and weather or atmospheric conditions.

A larger and heavier aircraft must displace more air and create more lift to sustain flight, compared with small, light aircraft. Therefore, they will create sonic booms stronger and louder than those of smaller, lighter aircraft. The larger and heavier the aircraft, the stronger the shock waves will be.

NASA says that a typical sonic boom for the F/A-18 is about 1.4 psf and a different NASA page goes on to say:

Overpressure Sonic booms are measured in pounds per square foot of overpressure. This is the amount of the increase over the normal atmospheric pressure which surrounds us (2,116 psf/14.7 psi). At one pound overpressure, no damage to structures would be expected. Overpressures of 1 to 2 pounds are produced by supersonic aircraft flying at normal operating altitudes. Some public reaction could be expected between 1.5 and 2 lb. Rare minor damage may occur with 2 to 5 lb overpressure.

As overpressure increases, the likelihood of structural damage and stronger public reaction also increases. Tests, however, have shown that structures in good condition have been undamaged by overpressures of up to 11 lb. Sonic booms produced by aircraft flying supersonic at altitudes of less than 100 feet, creating between 20 and 144 lb overpressure, have been experienced by humans without injury.

Damage to eardrums can be expected when overpressures reach 720 lb. Overpressures of 2160 lb would have to be generated to produce lung damage.

Typical overpressure of aircraft types are:

• SR-71: 0.9 lb, speed of Mach 3, 80,000 feet
• Concorde SST: 1.94 lb, speed of Mach 2, 52,000 feet
• F-104: 0.8 lb, speed of Mach 1.93, 48,000 feet
• Space Shuttle: 1.25 lb, speed of Mach 1.5, 60,000 feet, landing approach

They also include a graphic that shows the difference in sonic boom between the F-18 and the Concorde, with the Concorde having a much greater sonic boom at the same alittude:

Glass. Poorly mounted, undamaged glass in the greenhouse was chipped by impact against nail holding points at a sonic boom overpressure of 12.1 psf. The same type of glass, which was already damaged, was further damaged at a designed overpressure of 7.9 psf. A large one-ninth of an inch thick window, intentionally precracked from corner to corner, was further damaged by booms of an average 6.5 psf overpressure.

So typical sonic booms generated by normal aircraft aren't going to create anywhere close to the 12.1 psf that they say is needed to chip "poorly mounted" glass, but the strongest sonic booms can get well over this.

Tags
• generated by a B-1 Lancer or perhaps Concorde, which are several times larger than the F/A-18? Logically it seems that since you are displacing more air, the energy wave should have more energy. Then again, the plane isn't going any faster, so perhaps the surface area of the wave would be larger (because of the larger plane) but you wouldn't actually have any more energy at any given point? Anyone know if a bigger plan than the F/A-18 would have a higher energy sonic boom? And could that cause glass to break? Bonus point: A mathematical formula showing why, I love those things. For those

• that the aircraft went that way. In reality, this would be more complicated. For example, the plane most probably did not go along a straight path at max speed. However, useful inferences can be made by adding other...I had posted the question below on a New York Times article, but did not get any useful replies. The series of six successful Inmarsat pings known to exist, MAY carry enough information to say if the plane most likely went along the S or the N arc we see in reports. Unfortunately, only the last ping (at 8:11AM) is available publicly. Here is the basic idea on extracting the information

• WWII. They didn't have flight control computers back then, and the only control complaints I recall them having is that early versions had a tendency to flip over backwards when approaching stall speeds, well, that and the ground effects were pretty strong. But, no mentions of going into flat spins when going into hard maneuvers (that I recall). So how do they control that Y axis on flying wings? Are they perhaps more susceptible to a flat spin than a regular design (even if those risks can be kept to an acceptable minimum)?

• Is there a Canadian law or regulation which requires me to have my Radiotelephone Operator's Restricted Certificate (Aeronautical) on-board the aircraft with me? This is what I've found so far... service only where the person holds an appropriate radio operator certificate [...] However, I can't find a regulation saying I need the piece of paper with me. An example of the wording Canada uses in its regulations to say that you need to actually have the document with you is at CARS 401.03 (1)(d) (regarding pilot licences): the person can produce the permit, licence or rating

• was that this was dangerous to flight operations, and could have resulted in disaster had there been any emergency on-board during the event. Also, that this could result in an unruly cabin environment where in-flight safety of the crew and passengers would be affected. Were the actions (suspension of pilots and showcause notice to the airline) justified? Is a dancing cabin crew dangerous... organize such dance sequences to celebrate special festivals (since festivals are a huge part of Indian culture, plus publicity for the airline afterwards). Here is a YouTube video. One

• beneath the mid-Atlantic. Even after the recovery, there were concerns one of the drives had failed. That ACI episode also mentioned that the Airbus A330-203 in that accident came equipped with a system... to the cloud or a remote location either in lieu of or in addition to the physical devices installed in commercial aircraft. I would think this would be an accident investigator's dream come true... have any idea if there are plans for CVR and FDR data to be transmitted and recorded to the cloud or a remote location?

• 370 and Air France Flight 447 would have both been greatly aided if these floaties were in those planes. What do you think? ...Without getting into the mess of redesigning existing Flight Data Recorders, I have a simple proposal that I think would help in deep water crashes. I propose that several floating cushion sets... into the water, if the plane breaks up, then several of the cushions would float to the surface. When the cover dissolves, several folded arms open up making it much bigger exposing a orange-nylon

• In the US, the FFDO programme trains and permits pilots to carry a firearm in the cockpit. Do any other countries have a similar programme?

• Recently I was checking in to a flight and was asked if I'd like a window or aisle seat as usual and choose a window seat. I was then told that there are no more window seats available but I could get an aisle seat without someone sitting next to me and then just take that window seat. The plane was an ATR-72 so the rows were 2+2 seats. I know about weight distribution to the front/back but I couldn't come up for a good reason to do this. What could be the reason for not giving me that apparently free window seat right away?

• In As the Pro Flies, John R. Hoyt writes (pages 41-42): Suppose we have to land in high, gusty winds. That's what happened to Pilot Z, who once landed his plane during such conditions with his flaps down. After the wheels were on the runway he relaxed, never realizing that a plane is not landed until the switches are cut. Because he still had airspeed and because full flaps lowered..., a condition aptly described as dis-gusted. He would have dropped back on the runway, had not an alert co-pilot opened the throttles and saved both the day and the landing gear. He goes

Data information