GVII - ACN/PCN Rule of Thumb
Figuring aircraft and pavement classification numbers is similar to other Gulfstreams with the exception of determining if your Equivalent Single Wheel Loading (ESWL) is sufficient. As with many things GVII, our process is simpler. Let's look at the difference in that, as well as develop an easy rule of thumb for ACN/PCN. For a primer on all things ACN/PCN, see ACN/PCN.
The bottom line on ACN versus PCN is that the ACN represents how hard the airplane is pressing against the pavement and that the PCN is how hard the pavement pushes back. You want the ACN to be less than or equal to the PCN.
G500 ACN versus PCN
Photo: G500 flexible pavement ACN, G500 AOM, §06-01-00, figure 2.
You cannot determine the ACN before you know the PCN, because the PCN includes the pavement type, subgrade strength, and tire pressure. Unlike older Gulfstreams, we do not have the option of reducing tire pressure to lower our ACN. As an example, let's consider TQPF in Anguilla, which has a PCN of 22/F/A/W/T. The "F" means a flexible pavement, the "A" means a high subgrade strength, the "W" means the pavement can take tires of unlimited pressure, and the "T" means all this was determined through technical analysis. We have two charts to consider:
Photo: G500 rigid pavement ACN, G500 AOM, §06-01-00, figure 3.
We use the first chart, since it is for flexible pavements. We use the bottom line "A" because it has a high subgrade strength. The "W" tire pressure means the chart qualifies. Note that if the PCN was based on a medium ("Y") or low ("Z") tire pressure we would not be able to use this pavement. Following the line upwards we see that even at 80,000 lbs. our aircraft has a lower ACN than the runway's PCN of 22, so we are good at any weight. Note also that on the other chart, our ACN can get as high as 28 on a subgrade of ultra low strength.
Rule of Thumb:
A G500's ACN will never exceed 28. You might be okay with PCNs below 28, but you will have to get into the charts to be sure.
So if I am going to an airport with a PCN of 28 or higher, I am good to go. Since TQPF was a 22, I needed to get into the charts but found I was still okay because the subgrade strength on a flexible pavement lowered my ACN to below 22.
Let's say we are considering an runway with a PCN of 18/F/A/W/T. In this case, we use the same line on the same chart, but we see that our weight will be limited to just under 68,000 lbs.
G600 ACN versus PCN
Photo: G600 flexible pavement ACN, G600 AOM, §06-01-00, figure 2.
You cannot determine the ACN before you know the PCN, because the PCN includes the pavement type, subgrade strength, and tire pressure. Unlike older Gulfstreams, we do not have the option of reducing tire pressure to lower our ACN. As an example, let's consider TQPF in Anguilla, which has a PCN of 22/F/A/W/T. The "F" means a flexible pavement, the "A" means a high subgrade strength, the "W" means the pavement can take tires of unlimited pressure, and the "T" means all this was determined through technical analysis. We have two charts to consider:
Photo: G600 rigid pavement ACN, G600 AOM, §06-01-00, figure 3.
Note that these charts are drawn backwards compared to the G500. If you are operating both aircraft, be mindful of this.
We use the first chart, since it is for flexible pavements. We use the bottom line "A" because it has a high subgrade strength. The "W" tire pressure means the chart qualifies. Note that if the PCN was based on a medium ("Y") or low ("Z") tire pressure we would not be able to use this pavement. Following the line upwards we see that the runway's PCN of 22, limits us to no more than 86,500 lbs. Note also that on the other chart, our ACN can get as high as 32 on a subgrade of ultra low strength.
Rule of Thumb
A G600's ACN will never exceed 32. You might be okay with PCNs below 28, but you will have to get into the charts to be sure.
So if I am going to an airport with a PCN of 32 or higher, I am good to go. Since TQPF was a 22, I needed to get into the charts but found I was still okay up to 86,500 lbs.