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RV Safety:  How do we compare?

Tedd McHenry, Webmaster
[This article was originally published in October, 1999.]

Some months ago on the RV List, there was an interesting discussion on the number of RV accidents in the NTSB database (U.S.).  This led to more discussion on the RV accident rate, vis-à-vis the accident rate for other light aircraft.  To calculate the RV accident rate, in accidents per 100,000 flying hours (the rate that the NTSB reports), I needed to know the number of RV accidents and the total number of RV hours logged in the same period.  The accident numbers are in the NTSB databaseóno problem there.  But to estimate the number of RV flying hours, I decided to survey members of the RV List itself, to see how much they flew over the same period, then multiply that number by the official Vanís estimate of the number of RVs flying.  The period under investigation was July 1998 to June 1999, inclusive.

This sampling method (voluntary self-reporting by RV List members) is far from random, so Iíll try to resist the temptation to draw firm conclusions.  Iíve included all the raw data in the table accompanying this article, along with the statistics I calculated from it.

The NTSB accident rates for GA aircraft in the USA, for 1998, are 7.12 accidents per 100,000 flying hours, and 1.35 fatal accidents per 100,000 flying hours.  This has been on a more-or-less steady decline since at least 1982 (the first year for which I have data), when the numbers were 10.90 and 1.99, respectively.

The fleet rate for all types of RVs in the period 1 July 1998 to 30 June 1999, as surveyed, is 10.8 accidents per 100,000 flying hours, and 1.5 fatal accidents per 100,000 flying hours.  This is based on the following data:
 

  • average flying hours in the period (as surveyed) of 107.8
  • 1811 RVs (all types) flying in the USA, as estimated by Vanís
  • 21 accidents, including 3 fatal accidents, in the NTSB database, for the period
  • But this may not tell the whole story.  Quite a few people reported the lifetime hours of their RV, which tells quite a different story.  While the 98-99 average, as reported, was 107.8 flying hours, the lifetime flying hours data averages 199.6 hours per year.  At that rate of flying, the RV accident rates drop to 5.8 accidents and 0.8 fatal accidents.

    So, which estimate more accurately reflects how much RVers actually fly?  If anyone has any ideas how to derive that from the data, Iíd like to hear them.  My gut feeling is that the reported lifetime rate is probably high.  Why?  Because of the self-reporting nature of the survey.  Those who are (justifiably) proud of the amount they fly are more likely to report than those who donít fly so much.  There is anecdotal evidence that suggests this is true:  quite a few of those who reported lifetime hours said that they thought they flew more than most.

    Warning:  what follows is my opinion only!  The data isnít random enough to draw firm conclusions.  I think the data suggests that the RV accident rate is pretty much in line with the GA rate.  While the 98-99 rate, as reported, is slightly above the GA average, the lifetime rate suggests a much better number.  Given the widely-accepted hypothesis that homebuilt accidents are quite a bit more likely in the first few hours of a new (or newly-acquired) homebuilt, all the data suggests that RVs are at least as safe as the GA average after that initial period.
     
     
    Database
    Number
    Type 98-99
    Hours
    Hours
    Total
    Age
    Years
    Life
    Rate
    1 4 97.0 600 5.17 116.1
    2 4 160.0      
    3 4 84.4      
    4 4   750 6.70 112.0
    5 4 80.0      
    6 4 88.0      
    7 4 75.0      
    8 4 100.0      
    9 4   516 2.45 210.9
    10 6 198.0 355 1.78 199.3
    11 6 161.8      
    12 6 95.0      
    13 6   90.5 0.64 142.4
    14 6   288    
    15 6A 120.0      
    16 6A 1365   5.83 234.0
    17 6A 68.0   2.61  
    18 6A 66.0      
    19 6A   550 1.75 314.7
    20 6A   60 0.41 147.0
    21 6A 220.0 487 2.17 224.7
    22 6A   259 0.88 294.5
    23 6A 46.0      
    24 8 65.0      

    Feet Average   107.8 483.7 2.8 199.6
    Standard Deviation   51.2 361.4 2.2 70.6

     


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