RobertL18C wrote:
Vs increase by 1.2x in a 45 degree bank level turn, so 1.3 x Vs gives minimal gust protection
Yes you 1.41*VS0 you mean? I can turn at 1.3*VS0 without stalling at 40deg level with 0fpm and 45deg with some 50fpm decent but 1.4*VS0 will do as well 
my point is not about precision for 5deg bank or 50fpm, ideally one should fly speeds 1/ that allow 38deg turns as they achieve lowest turn radius for any aircraft at without losing height or stalling (VS0/cos(38)) and 2/ allow flying level with minimum power for some reason
My guess this is about 1.3-1.4*VS0 (pure maths on an ideal power curve and turn geometry), I could be completely wrong on this but I never felt losing any aircraft at 1.3*VS0, even on 45deg turns (just don’t pull it to stomach), but maybe some types are more quirkier? if so I can’t imagine even someone flying them slower/faster speeds on max power in steep turns without being on the edge…
I practice steep turns level, decent, stalls at various speeds, I am sure accelerated stalls at min power speed are really nothing (they just sort themselves naturally) compared to those you get bellow 1.2*VS0 or above 1.5*VS0 due to high power spin yaw or spiral dive, again my guess this has to do with the natural power-speed stability in level/turn flying
Also, one has to think about this the same was as their best speed/config they use to fly pattern/landing (I had few traffic hit & miss in busy circuits, one with 60 deg bank angle at 1.3*VS0 and quick push down), I guess the same would apply to ground obstacles and scud running otherwise they have no clue how to fly the circuit…
45 degree bank level turn is 1.41G (1/cos theta), the square root of 1.41 is around 1.2, hence 1.2x Vs
RobertL18C wrote:
the square root of 1.41 is around 1.2, hence 1.2x Vs
So what speed I can use to turn 45deg level with enough gust/stall protection?1.4*VS0?
Isn’t the smallest radius turn, and we are definitely in thread drift now, at the G spot, which for your typical utility load factor of around 4 G is around 2 x Vs and 75 degree bank. Standard aircraft with a 3.8 G limit would bank at around 70 degrees and 1.9x Vs.
Using knots R=V2/11.3 x tan Theta, where Theta is angle of bank. The Super Cub has a 150 foot turn radius at 80 KTAS and 75 degree bank.
At a 38 degree bank and 45 KTAS the radius increases to 230 feet.
Admittedly the concept of the G spot or corner is part of evasive manoeuvre technique. While the score of the Bf109/F-W190 against the Cub L4 was largely in favour of the Germans, one L4 did manage to get a Bf109 to crash in a box canyon.
RobertL18C wrote:
Isn’t the smallest radius turn, and we are definitely in thread drift now, at the G spot, which for your typical utility load factor of around 4 G is around 2 x Vs and 75 degree bank. Standard aircraft with a 3.8 G limit would bank at around 70 degrees and 1.9x Vs.
Agree, but you will need lot of power (aircraft may not even have that much) and a good visible horizon to achieve that? also it sits at corners of G/V-envelope, so better done right, besides at 2*VS0 and 70deg, I will have to think twice about sideslipping, flaps, full control deflection, crossing control, available power, putting flaps, drop gear, g-limits and more importantly spatial disorientation…
RobertL18C wrote:
At a 38 degree bank and 45 KTAS the radius increases to 230 feet.
I think I will stick to this one, it should do for landing in 1150ft patch with 2300ft visibility and 460ft ceiling 
this should work for someone who can’t decide how tight manoeuvring is done between slow gliders (zero power and 0G) or fast jets (afterburner and 7G)
RobertL18C wrote:
Admittedly the concept of the G spot or corner is part of evasive manoeuvre technique. While the score of the Bf109/F-W190 against the Cub L4 was largely in favour of the Germans, one L4 did manage to get a Bf109 to crash in a box canyon.
Probably related to 0G versus 7G tight turns? or slow vs fast turns than tight vs wide ?
Do any normal GA types have enough power to do a +3.8G level turn?
I was not proposing that a g corner turn is a sensible technique! Just pointing out that a 38 degree bank does not provide the smallest radius turn.
A zero G turn is a hammerhead turn, also not sensible technique.
The L4 lured the Bf109 into a box canyon and used it’s smaller turning radius to be the only aircraft to exit.
I doubt your average sewing machine GA can sustain a 3.8 g level turn at 1.9 x Vs. Hence even WW2 fighters having bags of excess power.
Even benign types will depart into an incipient spin in a 2 g plus accelerated stall, and a turn is by definition an accelerated manoeuvre. Typical altitude loss of at least 500 feet, plenty of moose stall fatalities in the NTSB.
With the g envelope in mind, low level VFR in visibility below 5000m is precautionary landing territory, and the PPL lesson is carried out with limited flaps for the field survey, and gentle rate one turns at typically 70-80 knots.
RobertL18C wrote:
low level VFR in visibility below 5000m is precautionary landing territory, and the PPL lesson is carried out with limited flaps for the field survey, and gentle rate one turns at typically 70-80 knots.
The view I have is if visibility drops bellow 10 times turn radius, ground roll or distance to cruise climb above MSA, then simply one can’t continue flying VFR in any form and all options are in doubt: no circuit/landing, no turn back and no climb above MSA, ceilings seems tend to be irrelevant to this topic IMO and anywhere between 500ft-2000ft one is betting on his engine to stay alive
It seems to me rate1 turns at 80kts will be manageable at 5km visibility but will be tough on 1.5km visibility, it has a 800m turn radius using that V2/(11*tan(angle)) formula…
I flew low VFR in 2km vis/800ft cb few times, I find it hard to keep rate1 for visual circuit landing (and that was 6000ft runway) but for precautionary field survey, I guess rate1 turn would be highly advisable as one is mainly looking down outside rather than at his airspeed/attitude or the aircraft nose, I think landing in a 2000ft patch in 1.5km visibility & 500ft cb will require more decisive turns than rate 1 for precautionary survey & landing, but surely far sensible option than any form of en-route flying at high cruise speeds, even MSA climb/turn back at those speeds could be risky in low visibility…
Jacko wrote:
I certainly can’t think of a reason to fly faster in any moderately well-behaved airplane. Far from high workload, it is very relaxing.
Off_Field wrote:
Yes, I would rather be going at 1.3Vso than full bore in low viz.
For the 2nd time now, I am not promoting flying around in low viz at full chat….
What I AM saying is that I recall the stress/workload was HIGH on the couple of occasions I wanted to be on the ground as the viz decreased. It has been several years since these experiences and I cannot remember the exact speeds I flew at, I reduced power/speed but certainly it was not to a calculated 1.3Vs and it certainly was NOT relaxing flying!! I do remember that the second time over North France, I was way more organised, proactive, and calm than the first time over the Po Valley in Italy, but then the situations were different and no doubt the first experience changed how I reacted in the second and I was earlier in my decision to divert and get on the ground.
Regards, SD..
Well one has to define low visibility & ceiling & terrain? IMO anything bellow 5km & 1500ft & 10% terrain gradient is no-go for VFR en-route above 100kts cruise in clean config, the numbers just don’t tie up
Beyond that is “VFR scud running”, basically an extended downwind leg to land nearby and has to be flown with such mindset: gear down, 1/2 flaps, fuel pump on, trim 1.3*VS0 and handoff then workload is zero but proceed with caution and not for 1h…
Visual circuits can be done safely at lower minima than 5km/1500ft but it will very tight in 1.5km/500ft even in slow wooden & fabric, one can still use those days as excuse for local circuit flying (but let be honest here an SR22 can’t get away with “VFR in 1.5km/500ft weather” without pressing parachute red button or the instrument auto-pilot buttons or landing in a long runway, he was number 2 that day )
If one adds mitigating risk of engine failure to VFR scud running one will be more careful about terrain and precautionary or diversion landing options, this also applies for en-route IFR flying or VMC on top, how much ceiling & visibility & terrain one is happy with? those who can fly IFR have the luxury to climb above MSA and continue flying on a proper plan (but then best defence against weather at destination is to have enough fuel for out-return and “test the weather” on a nearby ILS runway)
In gliders, one starts slowing down and look for fields when bellow 1500ft agl, you can’t stretch ahead unless terrain looks beautiful with more landing options or it is your home base within gliding range, same thinking should apply for power flying bellow 1500ft agl if the engine fails
