<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>sirk1882</author><text>It has to do with air density.&lt;p&gt;Heavy, cold air will generate more lift since it&amp;#x27;s &amp;quot;thicker&amp;quot; for lack of a better term.&lt;p&gt;Hot air is less dense. This means it takes more power to move more air.&lt;p&gt;It&amp;#x27;s easier to maybe think of the air that you breath as a &amp;quot;liquid&amp;quot; like material comprised of a mix of mostly nitrogen, some oxygen and a little carbon dioxide and other gases. That mix changes with temperature and elevation. Just like the deeper under the ocean that you go, you have more pressure, the lower to the ground you are the more atmospheric pressure you will feel. And the higher that you go, there&amp;#x27;s less pressure.</text><parent_chain><item><author>dmix</author><text>Sorry for the amateur question, but why does it take longer to take off in hot places? Doesn’t heat generate lift, like in gliders crossing hilly terrain? Or is it the heat offsetting with the cooler ground that helps, so you’d need a greater amount in hot places?</text></item><item><author>karlkatzke</author><text>3300 feet in balanced density conditions. You’d better not bet on 3300 feet in Phoenix during the day time most of the year. Or Denver for that matter.</text></item><item><author>_uy6i</author><text>3,300 feet in not a long runway - it means you can access ~80% of the ~5,000 runways in the US. On the the other hand A 777 needs 8,000-10,000 feet meaning it can only access &amp;lt;10% of US runways....&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.cia.gov&amp;#x2F;library&amp;#x2F;publications&amp;#x2F;the-world-factbook&amp;#x2F;fields&amp;#x2F;380.html&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.cia.gov&amp;#x2F;library&amp;#x2F;publications&amp;#x2F;the-world-factbook&amp;#x2F;...&lt;/a&gt;&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Boeing_777#777-200LR&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Boeing_777#777-200LR&lt;/a&gt;</text></item><item><author>karlkatzke</author><text>It seems to require a pretty seriously long runway to take off. On a warm day, we’re talking international airport length runway.&lt;p&gt;While pistons are cheaper than turbines, that’s because almost all of the approved pistons on the market use 1940s or earlier technology. They are very, very, very simple machines. They are still extremely expensive.&lt;p&gt;This engine is very complicated, even for an automotive engine. It’s got some revolutionary attributes, but it also has a bunch of single points of failure that would mean traveling in this airplane over long distances and large bodies of water isn’t a good idea.&lt;p&gt;I’m frankly not holding my breath. While they’ve got a bunch of buzz around them, that and a working example are like 1&amp;#x2F;10 the battle in the aircraft industry. Wish them the best for trying to advance the art but many more established and better funded folks have tried and gone bankrupt before them.</text></item></parent_chain></comment><story><title>The potentially revolutionary Celera 500L aircraft</title><url>https://www.thedrive.com/the-war-zone/36016/the-potentially-revolutionary-celera-500l-officially-breaks-cover</url></story>
<instructions>Your goal is to analyze the following comment and estimate how highly it will be upvoted by the Hacker News community.</instructions><comment><author>unoti</author><text>&amp;gt; why does it take longer to take off in hot places?&lt;p&gt;When the air is cold the air is more dense.  This has an impact both on how much lift is generated per amount of speed over the wings, and also impacts how much power the engine&amp;#x2F;carburetor are able to generate.</text><parent_chain><item><author>dmix</author><text>Sorry for the amateur question, but why does it take longer to take off in hot places? Doesn’t heat generate lift, like in gliders crossing hilly terrain? Or is it the heat offsetting with the cooler ground that helps, so you’d need a greater amount in hot places?</text></item><item><author>karlkatzke</author><text>3300 feet in balanced density conditions. You’d better not bet on 3300 feet in Phoenix during the day time most of the year. Or Denver for that matter.</text></item><item><author>_uy6i</author><text>3,300 feet in not a long runway - it means you can access ~80% of the ~5,000 runways in the US. On the the other hand A 777 needs 8,000-10,000 feet meaning it can only access &amp;lt;10% of US runways....&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.cia.gov&amp;#x2F;library&amp;#x2F;publications&amp;#x2F;the-world-factbook&amp;#x2F;fields&amp;#x2F;380.html&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.cia.gov&amp;#x2F;library&amp;#x2F;publications&amp;#x2F;the-world-factbook&amp;#x2F;...&lt;/a&gt;&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Boeing_777#777-200LR&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Boeing_777#777-200LR&lt;/a&gt;</text></item><item><author>karlkatzke</author><text>It seems to require a pretty seriously long runway to take off. On a warm day, we’re talking international airport length runway.&lt;p&gt;While pistons are cheaper than turbines, that’s because almost all of the approved pistons on the market use 1940s or earlier technology. They are very, very, very simple machines. They are still extremely expensive.&lt;p&gt;This engine is very complicated, even for an automotive engine. It’s got some revolutionary attributes, but it also has a bunch of single points of failure that would mean traveling in this airplane over long distances and large bodies of water isn’t a good idea.&lt;p&gt;I’m frankly not holding my breath. While they’ve got a bunch of buzz around them, that and a working example are like 1&amp;#x2F;10 the battle in the aircraft industry. Wish them the best for trying to advance the art but many more established and better funded folks have tried and gone bankrupt before them.</text></item></parent_chain></comment><story><title>The potentially revolutionary Celera 500L aircraft</title><url>https://www.thedrive.com/the-war-zone/36016/the-potentially-revolutionary-celera-500l-officially-breaks-cover</url></story>