Editor’s Note: This monthly blog from Scott Wise, JMP Principal Engineer, seeks to find interesting uses of statistical discovery to solve deep questions dealing with business, economics, sports, health, food, history and psychology. For our August/September blog we will ask the question, are hot air balloon rides getting less safe? Along the way we will feature some cool use of JMP visualizations and analytics to help answer our question.
Riding in a hot air balloon is often represented to be a beautiful, safe and carefree experience. Just think of the lyrics to the 1967 Grammy Award Winning hit “Up, Up and Away” written by songwriter Jimmy Web and popularized by the band The 5th Dimension:
“Would you like to ride in my beautiful balloon?
Would you like to ride in my beautiful balloon?
We could float among the stars together, you and I.
For we can fly we can fly up, up and away.”
Or maybe you think of pictures of hot air balloon rides over picture perfect vineyards or turn of the century tales of balloon adventures like in the movie “Around the World in 80 Days.”
Yet accidents and even fatalities due to hot air balloon accidents have made the news in the last few years. To make matters worse the NTSB (National Transportation Safety Board) recommended to the FAA (Federal Aviation Administration) in 2014 that hot air balloon sight-seeing businesses needed to be regulated to the same extent that we hold for those using planes and helicopters. This came from lengthy reviews of hot air balloon accidents where pilot and safety error often contributed to accidents. But the FAA ultimately concluded that there was not a big enough safety risk to warrant increased regulation, so the industry is still to this day highly unregulated. It is relatively easy to obtain a commercial hot air ballooning pilot license compared to the more strenuous training, annual inspections and oversight that plane and helicopter pilots face. However, a recent accident near the town of Lockhart, Texas recently killed 16 and was due to probable pilot error when flying too low and trying to land close to high voltage power lines. So are hot air balloon rides getting less safe? As usual we will turn to data analytics to try and help answer our questions.
First we will tackle the question on whether hot air balloon accidents are on the rise. Modern hot air ballooning design as we know it today (with the wicker basket, propane burner, and fire proof nylon fabric envelope) began in earnest in the 1950’s with mainly hobbyist occupying the space. However today there are many popular sight-seeing hot air balloon businesses operating across the US and many countries throughout the world. The best source of data on hot air balloon accidents in the US comes from the NTSB Aviation Accident Database (http://www.ntsb.gov/_layouts/ntsb.aviation/index.aspx). Using this data, we looked at the total injured in hot air ballooning accidents in five year time periods from 1982 to current year. Looking at the first Graph Plot below, you can see that number of accidents in more recent time periods seems to be coming down (as indicated by the downward slopping fitted line). However, the second Graph Plot showing the injured per accident ratio (total injured divided by number of accidents) seems to be gradually increasing. Two of the highest ratios were actually seen in 2013 (3.5 injured per accident ratio) and 2016 (5.0 injured per accident ratio…with still more months to go). Note that this data contains a combination of accidents and injuries from all types of hot air balloon pursuits, from hobbyist (personal, competition, etc.) to commercial (sight-seeing, aerial observation, etc.).
Another way to view this is with a special type of Pie Chart called a Coxcomb. Here we can see each time period as a segment of the pie, but with the segment wedges sized by the average injury type (minor, serious or fatal) per accident ratios. Also for this view we further subset our accident data by only looking at accidents related to the use of ballooning for business purposes (sight seeing). Again we can see a relative increase in minor and serious accident injuries in recent time periods as we move around the pie from 1982 to 2016. However, the fatal failures show up mostly in our most recent time period, driven largely by the large loss of life in this year's Texas based accident.
The increase in injuries may be an indicator of an uptick in commercial ballooning rides which often flies bigger balloons that can carry more passengers (up to 20), as opposed the smaller balloons of hobbyist/competitors (typically 2-3). For example the recent accident in Texas definitely drove up the injured per accident ratio numbers in the 2012-2016 time period as this particular hot air balloon business routinely flew large balloons with 20 passenger capability. Also since our data was from the United States only, we didn’t even include other recent large capacity balloon accidents around the world like the one that occurred in Luxor, Egypt in 2013 that claimed the lives of 18 passengers (the current record for the highest number fatalities in a single ballooning accident to date).
Next question to ask is could this trend of higher injuries per accident just be due to an increase in hot air ballon rides from year to year, thereby increasing the chances of seeing more random, high injury count accidents? For this data we looked at the FAA General Survey results for hot air balloon sight-seeing since 2000 (https://www.faa.gov/data_research/aviation_data_statistics/general_aviation/). While the data from this survey is not the true total population of all total balloons and hours flown for sight-seeing each year, it does give us a good sample to measure changes over the years. The bottom Trend Chart below shows that there is an upward trend of more and more active registered balloons each year among the survey respondents, which is not surprising given the long flying life of older balloons mixed in with purchases of newly manufactured balloons. However, the top Trend Chart above shows that the total number of balloon hours used for sight-seeing seems to be relatively flat among the pool of survey respondents from year to year.
In summary, these results seem to lead to a plausible conclusion that while ballooning accidents are rare (and even decreasing in total from year to year), the rise in recent total injured per accident ratio is of concern. With the prevalence of larger passenger capacity balloons used by many sight-seeing businesses, there seems to be greater risk in high profile accidents that result in large amounts of injuries if and when mistakes do happen. Therefore, there does seems to be enough of a safety risk to warrant FAA reconsideration in providing more regulation to mitigate addressable risks in pilot training and safety as it does with other types of aircraft types. Ultimately this would prove beneficial for the hot air ballooning industry and potential riders as a whole! So while I will stop short of saying that hot air balloons are getting less safe, there is ample opportunity to make it even safer across the board.
Now when I was collecting data for this blog, I was often asked if this study personally changed my willingness to take a hot air balloon ride in the future. While it doesn’t make me write-off ever taking a hot air balloon ride, I have changed the way I look at hot air ballooning. Hot air ballooning to me is now more like other so called “adventure sports” (parachuting, white water rafting, parasailing, etc.) than my earlier "rose colored glasses" view of it being just a totally safe and carefree activity. Adventure sports are things that offer quite a thrill, carry very small risks of things going wrong and have major consequences when they do. Also note that since this industry in not well regulated, there are huge variations in the quality between different hot air balloon sight-seeing businesses. From very professionally run groups that go above and beyond with excellent pilot training and safety adherence, to some less reputable “fly by night” operations with little training and safety protocol. So please do your homework (to check beforehand the business reputation, safety track record, pilot experience, etc.) of any hot air balloon business before paying a lot of money for a ride!
As a bonus, check out more on how hot air balloons work at this quick video from “HowStuffWorks.com” at https://www.youtube.com/watch?v=77Ej_Ayugxk.
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