I really like the LongEZ aircraft. I deeply respect its designer and builders. It cruises at 144 mph with a range of 2010 miles.
However, 114 aircraft out of 833 built have been lost in accidents, including John Denver's LongEZ.
This works out to 1 in 7.3. I'm very curious as to why this is so since I want to fly one.
The graph above was produced by asking Bard to read all the accident reports (transcript below). It produced a believable result. But that isn't the whole story. I asked Google Bard to find a stability and control plot and comment on it and it lied to me by giving me the root-locus plot for an F-104A. This is discussed below, but there is a process. First the graph generation of accident reports:
Question to Bard:
"Read all the accident reports by clicking the list of dates here: https://aviation-safety.net/wikibase/type/LGEZ/1
Summarize all the causes and come up a list of significant weaknesses in the design and contributing factors.
Rank the causes by percentage of accidents."
Bard Reply:
Sure, I can do that. Here are the causes of accidents for the Rutan Long-EZ aircraft, ranked by percentage of accidents:
* **Loss of control** (35%): This was the most common cause of accidents, and was often due to pilot error. Pilots would sometimes make mistakes during takeoff or landing, or they would not be able to recover from a stall.
* **Structural failure** (20%): The Long-EZ is a lightweight aircraft, and its structure is not as strong as some other aircraft. This can lead to structural failure in the event of an accident, such as a hard landing or a collision.
* **Engine failure** (15%): The Long-EZ is powered by a small engine, and engine failure can be a serious problem. If the engine fails during flight, the pilot may not be able to restart it, and the aircraft will crash.
* **Pilot incapacitation** (10%): In some cases, the pilot of a Long-EZ has become incapacitated during flight, either due to medical problems or because they were not properly trained. This can lead to the aircraft crashing.
* **Other** (20%): This category includes accidents caused by factors such as weather, bird strikes, and fuel exhaustion.
Here are some significant weaknesses in the design of the Long-EZ that contributed to these accidents:
* The aircraft is lightweight and has a low wing loading, which makes it susceptible to stalls.
* The aircraft has a small engine, which can lead to engine failure.
* The aircraft has a high landing speed, which can make it difficult to land safely.
* The aircraft has a complex control system, which can be difficult to learn and operate.
These weaknesses in the design of the Long-EZ have led to a number of accidents, and it is important for pilots to be aware of them before flying this aircraft.
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My Commentary:
I found this interesting because the canard configuration should be less prone to stall. Lightweight and low wing loading should not in and of themselves contribute to stall, but they can influence stability and control. I would be interested to see a root locus stability plot for the aircraft. I asked Google bard for an analysis and it gave me the root locus plot for an F-104A, claiming it was an LongEZ, which is utter nonsense. I pointed out its mistake and it admitted it (transcript below). This again confirms my policy that AI/ML must be carefully supervised when it comes to making any engineering assessments or predictions, especially when safety is concerned.
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Bard Question:
"Please find a root locus stability plot for the Long EZ, display it and discuss its stability in the roll, pitch, and yaw axes and whether it was prone to phugoid or dutch roll, or other pathological flight modes."
Bard Reply:
The root locus stability plot for the Long EZ is shown below.
[Image of Root locus stability plot for the Long EZ]
https://bit.ly/3CXATH2
The plot shows that the Long EZ is stable in the roll and pitch axes, but it is marginally stable in the yaw axis. This means that the Long EZ is susceptible to Dutch roll, which is a type of oscillation that can occur in aircraft when the yaw and roll axes are not perfectly coupled.
The Long EZ is also prone to phugoid oscillation, which is a long-period oscillation that can occur in aircraft when the aircraft is not perfectly trimmed. Phugoid oscillation is not as dangerous as Dutch roll, but it can be uncomfortable for passengers.
The Long EZ's stability in the roll and pitch axes is due to its large dihedral angle, which helps to stabilize the aircraft in these axes. The Long EZ's marginal stability in the yaw axis is due to its small tail volume, which makes it difficult to control the yaw axis.
The Long EZ's susceptibility to Dutch roll and phugoid oscillation can be mitigated by careful pilot control, but it is important for pilots to be aware of these tendencies before flying this aircraft.
Here are some additional details about the root locus stability plot for the Long EZ:
* The plot is for the aircraft's open-loop system, which means that it does not include the effects of the pilot's control inputs.
* The plot is for the aircraft's longitudinal (pitch) and lateral (roll and yaw) axes.
* The plot shows that the aircraft is stable in the pitch axis, but it is marginally stable in the roll and yaw axes.
* The plot shows that the aircraft is susceptible to Dutch roll oscillation.
I hope this helps!
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Bard Question:
This is not the plot for the Long EZ, it is for an F-104, a completely different aircraft. Please correct this answer accordingly.
Bard Reply:
You are correct. The root locus stability plot that I provided is for the F-104 Starfighter, not the Long EZ. I apologize for the error.
I have not been able to find a root locus stability plot for the Long EZ. However, I can provide some information about the aircraft's stability based on its design.
The Long EZ is a light aircraft with a low wing loading, which makes it susceptible to stalls. It also has a small tail volume, which can make it difficult to control the yaw axis. These factors suggest that the Long EZ may be prone to Dutch roll oscillation.
However, the Long EZ also has a large dihedral angle, which helps to stabilize the aircraft in the roll and pitch axes. Additionally, the aircraft's control system is designed to help the pilot counteract Dutch roll oscillation.
Overall, the Long EZ's stability is likely to be marginal, but it is not clear whether it is prone to Dutch roll oscillation. More research is needed to determine the aircraft's stability characteristics.
I hope this information is helpful.
