Oh hai. How time flies - you take a wee blog break & before you know it, a couple of months have passed. But, yes, this thing is still on.
It's been even longer - over eight years - since I did an Aircraft of the Day. And I only ever did two of 'em, anyway (here's the other). So here, by total absence of popular demand, is another, the aeroplane I've been obsessing about most recently, a 1930s design, the Mignet Pou-du-Ciel, better known to anglophones as the Flying Flea:
Henri Mignet's concept was simple. A small, basic home-built aircraft which could be constructed by anybody with a few craft skills and safely flown by a novice pilot. It was meant to bring aviation to the masses in the same way that Ford's Model T had brought motoring to the masses. Indeed, according to the Wikipedia article the name Pou-du-Ciel ("sky louse") was a nod to the Model T:
The Pou's unusal design, more like a two pairs of wings than a conventional wing and horizontal tailplane was intended to be a safety feature. The tandem-wing design was designed to be stall proof,* as explained here:
All great. Unfortunately, Mignet's HM.14, the original Pou, had an unsuspected design flaw which caused the aircraft to pitch nose downward when pilots attempted to recover from a shallow dive. A series of fatal accidents meant that, instead of becoming known as the safe, reliable "people's aeroplane" the Pou ended up with a reputation as a death trap - for example it makes 9th place on Hush Kit's list of the 10 Worst French Aircraft (just over 4 mins into this vid)
After these crashes all Pous were grounded by the authorities in France and the UK, pending investigations. The accident investigations were aided by the diminutive size of the Pou - small enough to fit inside wind tunnels which were usually only big enough to accommodate a scale model of the aircraft being tested. Testing revealed that, at certain angles "the front wing's downwash would accelerate the air over the rear wing and cause it to gain lift more quickly than the front wing, resulting in an ever-increasing nose pitch-down and flight directly into the ground."
The good news was that, once diagnosed, the problem was easy to fix, by simply moving the rear wing six inches backwards. But by the time modified, safe Pous were taking to the air again, it was 1939 and hobby fliers in France and the UK would soon have more pressing concerns on their minds than joy-riding in tiny home-built planes.
There's a bit of a "what if" hanging in the air here. What if the original Pou design flaw had been spotted before people started building and flying them? What if the war hadn't intervened when the design had been perfected?
I don't think we'd have seen huge swarms of Pous in the skies. It was only ever a one, or two seat pleasure craft, a really cool hobbyists' project, as opposed to a practical form of transport. Moving back from alternative history to real history, flight did eventually become more egalitarian, but not in the way Mignet anticipated. Instead of ordinary people taking to the skies en masse in tiny home-built machines they could construct or buy relatively cheaply, ordinary people got airborne once seats on huge, complex multi-million dollar jets became affordable to people outside what they used to call the "jet set."
The future doesn't always work out the way we expect. Although I do have a sort of yearning for Mignet's original vision - there's something about the simplicity, the minimalism and the do-it-yourself ethos that makes me wish for a Wallace and Gromit world where folk spend their weekends making their own aircraft or flying them around their neighbourhood. Although in an age where a mere radio-controlled drone, or possibly just the rumour of one, can shut a major international airport, that's probably more whimsical than wise.
*A concern shared by Juan de la Cierva, who had invented the autogyro in the previous decade in another successful attempt to devise a stall-proof aircraft. Some irony fans like to say that De la Cierva was killed when the conventional plane he was travelling in stalled in 1936, but a quick visit to Wikipedia debunks this neat story - it looks as if the aircraft drifted off course while taking off in foggy weather, accidentally flew into the chimney of a house on some high ground adjacent to the aerodrome and crashed.
It's been even longer - over eight years - since I did an Aircraft of the Day. And I only ever did two of 'em, anyway (here's the other). So here, by total absence of popular demand, is another, the aeroplane I've been obsessing about most recently, a 1930s design, the Mignet Pou-du-Ciel, better known to anglophones as the Flying Flea:
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| Mignet HM.14 Pou-du-Ciel |
The odd name comes from the French nickname for the Ford Model T automobile, "Pou de la Route" or "Louse of the Road" because Henry Ford's economy car was so common and initially came only in black.Which might be true, although my brief attempts to find a direct source confirming that the French ever called Model Ts "road lice" has drawn a blank so far (although a Belgian car site does seem to suggest that what looks like a post-war microcar, Hippolyte Delimal's Carabe was also nicknamed the "Pou de la Route" - presumably named after the Pou-du-Ciel, which isn't a lot of help, either entomologically or etymologically).
The Pou's unusal design, more like a two pairs of wings than a conventional wing and horizontal tailplane was intended to be a safety feature. The tandem-wing design was designed to be stall proof,* as explained here:
The wing enters a stall. But here, in tandem wing configuration, the front wing will stall. What happens now? Well, the nose drops a bit. The rear wing is still holding the airplane up a bit. But it cannot hold it completely, so the airplane will sink while its nose drops a bit. But, the nose that did drop makes the angle of the airplane (and its wings) less, so ...the wing lifts again once the angle of the airplane is good enough. The nose rises again. You get another change to react to the stall.Also, the controls for the all-moving front wing and rudder were simpler than those for a conventional aircraft (just a control stick, no rudder pedals), making life easier for a rookie pilot.
The result is that you enter a wave like movement, you sink while you have your nose going down and up again. You can keep on to this situation and even use it as a kind of hard controlled descent. Or you can get more time to react to this situation and give more power or lower your nose. Anyway, you are given a chance to live and tell.
All great. Unfortunately, Mignet's HM.14, the original Pou, had an unsuspected design flaw which caused the aircraft to pitch nose downward when pilots attempted to recover from a shallow dive. A series of fatal accidents meant that, instead of becoming known as the safe, reliable "people's aeroplane" the Pou ended up with a reputation as a death trap - for example it makes 9th place on Hush Kit's list of the 10 Worst French Aircraft (just over 4 mins into this vid)
After these crashes all Pous were grounded by the authorities in France and the UK, pending investigations. The accident investigations were aided by the diminutive size of the Pou - small enough to fit inside wind tunnels which were usually only big enough to accommodate a scale model of the aircraft being tested. Testing revealed that, at certain angles "the front wing's downwash would accelerate the air over the rear wing and cause it to gain lift more quickly than the front wing, resulting in an ever-increasing nose pitch-down and flight directly into the ground."
The good news was that, once diagnosed, the problem was easy to fix, by simply moving the rear wing six inches backwards. But by the time modified, safe Pous were taking to the air again, it was 1939 and hobby fliers in France and the UK would soon have more pressing concerns on their minds than joy-riding in tiny home-built planes.
There's a bit of a "what if" hanging in the air here. What if the original Pou design flaw had been spotted before people started building and flying them? What if the war hadn't intervened when the design had been perfected?
I don't think we'd have seen huge swarms of Pous in the skies. It was only ever a one, or two seat pleasure craft, a really cool hobbyists' project, as opposed to a practical form of transport. Moving back from alternative history to real history, flight did eventually become more egalitarian, but not in the way Mignet anticipated. Instead of ordinary people taking to the skies en masse in tiny home-built machines they could construct or buy relatively cheaply, ordinary people got airborne once seats on huge, complex multi-million dollar jets became affordable to people outside what they used to call the "jet set."
The future doesn't always work out the way we expect. Although I do have a sort of yearning for Mignet's original vision - there's something about the simplicity, the minimalism and the do-it-yourself ethos that makes me wish for a Wallace and Gromit world where folk spend their weekends making their own aircraft or flying them around their neighbourhood. Although in an age where a mere radio-controlled drone, or possibly just the rumour of one, can shut a major international airport, that's probably more whimsical than wise.
*A concern shared by Juan de la Cierva, who had invented the autogyro in the previous decade in another successful attempt to devise a stall-proof aircraft. Some irony fans like to say that De la Cierva was killed when the conventional plane he was travelling in stalled in 1936, but a quick visit to Wikipedia debunks this neat story - it looks as if the aircraft drifted off course while taking off in foggy weather, accidentally flew into the chimney of a house on some high ground adjacent to the aerodrome and crashed.
1 comments:
The good news was that, once diagnosed, the problem was easy to fix, by simply moving the rear wing six inches backwards
That's easy to deduce from the maths:
https://www.sciencedirect.com/topics/engineering/pitching-moment-coefficient
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