Primarily for general aviation discussion, but other aviation topics are also welcome.

I've flown most of the current high end microlight trainers, including the Alpha - which really impressed me as a potential training aeroplane. But, having all about the same weight and powerplant, they all have about the same performance - being usually around 90-110kts IAS cruise, a service ceiling around the 12,000ft mark and needing around 200m of runway.

Which sipping MOGAS around 15-20 litres/hr is pretty impressive, just not that impressive.

When is a microlight not a microlight?

On the premise of EASA new basic regulation, permitting for MTOM of 600kg for microlights in Europe, Germany was the first country to implement the new regulation. As a testament to excellent collaboration between DULV and Pipistrel since decades, Pipistrel became the first to obtain new microlight certification according to new German 600kg technical LTFUL 2018 rules.
The handover event of the certification document was organized at the AERO Friedrichshafen fair in Germany on Wednesday, 10. April 2019. ... hafen-2-2/
Which microlight is that?

I think it was something I picked up in a Wikipedia entry. Which only goes to show you should never believe anything you read on the Internet....

The Virus SW, presently sold as LSA type, but weighing in at 600Kg, gives a VNE of 163Kt. Note the Va is around 116Kt. Interesting if the UK microlight weight is increased.

This from the Pipistrel SW POH:

This from the Pipistrel Virus POH:
Va is the stall speed multiplied by the square root of the g-limits. With a 4g limit, which is pretty normal, that gives you a stall speed of 58 knots. If it had the standard 3.8g limit for light aeroplanes, a stall speed of 59.5 knots.

Unless it has a phenomenal high lift landing flap system, that is never going to be a microlight. Microlights require a stall speed not above 35kts, and VLA class aeroplanes 45 knots with land flap.


Looking at the Virus SW POH it actually says cruise speed 116kts.
That presumably means Vno?
I have the same with the Kitfox - Vno claimed 95kts but Va only 70kts.
I have tried various sources and not found a good definition for Vno and confusion with Va seems not uncommon.
Can you provide enlightenment please?
BTW it says Vfe 40kts.

Fred Drift

Edit - further into the POH it says Va 94kts, Vra 135kts, it doesn't give Vno and it doesn't mention 116kts again. More confusion (at least for me!)
Certainly an impressive little machine though.
I was just going with the data on here, and not any official document.

Va = "Manoeuvre speed", this is the speed where the stall speed curve reaches the positive g limit. On lighter aeroplanes, it's also commonly given as the MAXIMUM speed for flight in rough air. On virtually all aeroplanes it's also normally and correctly given as the maximum speed for full and sudden application of the primary flight controls. Whilst engineers will know it in CAS (Calibrated Airspeed), pilots shouldn't really be interested in anything other than IAS (Indicated Airspeed).

Vc = Design cruising speed. It has absolutely no relevance to a pilot, and ideally should not even be mentioned in the manual. It is a figure, calculated by reference to various design and flight test parameters used in airworthiness calculations. It is usually faster than the aeroplane is actually capable of cruising. Normally only given in CAS.

Vno = Maximum normal operating speed in IAS; it's a guidance figure developed by the certification team and you are *advised* not to fly faster than that normally. For smaller aeroplanes there is no formal definition, but *if* declared it usually gets put around 80-90% of Vne, which in turn is usually 90% of Vdf (maximum speed seen in flight testing safely) which in further turn must be no greater than Vd (design structural limiting speed). Engineers do all this in CAS, but then give it to pilots in IAS.

Vh = maximum achievable speed in level flight with maximum continuous power. This is worth knowing, and has both piloting and certification uses. Pilots want to know it in IAS, engineers want to know it in CAS. BCAR Section S has a long perpetuated error where it calls Vh, Vc confusing anybody not really familiar with these rules.

Cruising speed can be a bit of an abstract concept (as opposed to Vc above), but is often quoted in sales material. It's probably most usefully quoted at specific combinations of altitude and power, and in True Airspeed (TAS), so you can use it meaningfully for flight planning purposes. Sales blurb usually quotes it near to the service ceiling, to make the aeroplane sound unrealistically fast, as the higher you are, the greater TAS for any given CAS.

A Vra that far above Va sounds utter cobblers to me. I would use the present Va as your Vra, or maximum rough air speed. An aeroplane that stalls at 4g/70kts is capable of pulling theoretically over 7g at 95kts in sufficiently severe turbulence. That is pretty unlikely - but why go there?

40 kts Vfe? That sounds stupidly low, how the heck do you fly an approach under 40 knots in, well, anything?

Va = "Manoeuvre speed", this is the speed where the stall speed curve reaches the positive g limit.

Apologies. Can you clarify the difference with “corner speed”. My understanding is minimum speed to achieve maximum G. I appreciate not entirely relevant to microlights.... :wink:
Human Factor wrote:
Va = "Manoeuvre speed", this is the speed where the stall speed curve reaches the positive g limit.

Apologies. Can you clarify the difference with “corner speed”. My understanding is minimum speed to achieve maximum G. I appreciate not entirely relevant to microlights.... :wink:

Who the heck is out there making up these terms when there are perfectly sound ones around since the 1930s and found in any textbook on aeronautical engineering.

Minimum speed to achieve maximum G is what Va is, I can see why looking at the diagram somebody might call it "corner speed", but people making up unnecessary extra terminology is not simplifying anything.

This isn't my diagram, I just found it online, and the g-limits and speeds vary between aeroplanes, but it shows it all pretty well. Airliners usually have N1=2.5g as shown here, light aeroplanes 3.8g, microlights 4g, aerobatic aeroplanes anything from 6g, fighters around 8g.


This isn't mine either, but shows the form of the diagram usually in documents like BCAR Section S and CS.23. It shows the formal notation of letters used correctly. It doesn't show Vne, but that should be at 90% of Vd (or a little lower if there are particular reasons to, but there usually aren't).


Dave W liked this
The US Navy seemingly...

Corner speed is an important factor of maximum turn performance. Corner speed is defined asthe minimum airspeed at which the maximum allowable g can be generated. At corner speed,the aircraft can attain its maximum turn rate. For our purposes, 280 KIAS is the T-2C cornerspeed. Below this speed, if you attempt to pull more "G", the aircraft will enter buffet and stallat its aerodynamic limit. This results in an increase in the turn radius and a decrease in the turnrate. On the other hand, if the aircraft is maneuvered above the corner speed, the max allowable"G" becomes the limiting factor. The excess airspeed (above corner speed) will result in a turnradius increase and a turn rate decrease.

Apologies for the thread drift....
Hmm, okay, I recognise that concept from my mispent youth doing stuff with fighters even if I'd forgotten the term, but that definition I'm pretty certain is wrong, even if it does come from the US Navy.

The concept of a speed for maximum turn rate has two versions, one stall limited for an instantaneous turn rate, the second thrust limited for a sustained turn. Neither of those are necessarily going to be at Va. This is a different concept, and not very relevant to those of us flying light puddlejumpers. It is also not the same as achieving maximum g.

This takes me back to plotting graphs at a certain establishment in Wiltshire from Jaguar flight test data.... ... 16-part-1/

I decided to see a spinal consultant privately and although this cost me £525 it was well worth it. On the basis of his very detailed 8-page report the CAA gave me another primary review and this morning I received an unrestricted class 2 medical. My FI course should be starting in the very near future.

Thank you to everyone (especially FD and Lobstaboy) for the invaluable advice and support I have been given by people on this forum.
PeteSpencer, rikur_, scd975 and 31 others liked this