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Approach Speed in GA Aircraft

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Approach Speed in GA Aircraft

Old 7th Sep 2020, 16:00
  #21 (permalink)  
 
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Well it does matter when you are flying commercially into short strips.
The Canadian CPL test requires candidates to calculate the stall speed in the landing configuration for the predicted landing mass.
Ex 2B in the Canadian Flight Test Guide: https://tc.canada.ca/en/aviation/pub...-tp-13462#ex2b
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Old 7th Sep 2020, 17:22
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But again, that is about a CPL, not about "private flying".
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Old 7th Sep 2020, 17:31
  #23 (permalink)  
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Your ability to track down the various iterations of the regs is impressive.
Thanks, my role as acting on behalf of Transport Canada to issue STC approval for modification requires me to be up on these small details. Some modification approval projects can be horribly cost burdened by having to show compliance to a more recent amendment of the design requirement or not. The determination process (for every STC project), known as Changed Product Rule decision, focuses on exactly which amendment of a particular design requirement will be applied. It can be item by item, as it was when I participated in the re-engine of the DA-42 to Lycoming. This is the "certification basis" for the STC. It's usually the same as that for the original type certificate, but not always. There are times where either the Engineers at TC, or I will propose to show compliance to a more recent amendment of a design requirement during certification, when doing so will result in noticeably improved safety.

I've done a fair amount of position error correction flying. I have a program coming up in a week or so on a AS350 helicopter with a previously approved external assembly, which is suspected of inducing a PEC error (static port partly obscured by the mod). My work to approve a new pitot tube and static port arrangement on the DC-3T's in Germany has been put off until next year. That will involve a lot of flying, and some fiddling with static ports to get within the required limits of error (it has too much right now to be approved, so the original system is still in use).

Interestingly, while I was test flying an older Cessna 210 last week, following a massive repair I had to approve, I noticed that the operation of the landing gear momentarily affected the static ports, and induced a bounce in the altimeter and VSI. After landing I had a look and noticed that Cessna had placed the static ports up and behind the main gear doors. Obviously, with the main gear doors open, there is a static disturbance. But, the doors close again after the gear extends, so it's not really a problem, as long as you're aware.

If the manual tells you to approach at 1.4Vs, for example, then OK. But if the manuals recommends 1.3 and your airclub 1.6, what then ?
Simple, you fly the aeroplane in accordance with the POH/AFM. No one including flying/schools/clubs or any other "operator" have the right to demand anything different.
Agreed. If the flying club/school.operator would like to have the airplane operated noticeably differently to what the flight manual/POH says, they should apply for an STC, with which they will get an approved Flight Manual Supplement for the operation they desire - if it's worthy of approval. A needlessly fast approach, if ever to be approved, would be accompanied with changed procedures, and performance data. Fly it the way the original flight manual/POH and any supplements describe.

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Old 7th Sep 2020, 19:15
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Jan - It is of no consequence whether the aircraft is flown by a commercial pilot for commercial operations or flown by a private pilot for private purposes: It is still the same aircraft and therefore it flies the same.

For the CPL skill test and throughout the training the operation of the aeroplane must be strictly in accordance with the aircrafts POH. Whether flown by a CPL or a PPL it is the deviations from the correct ops that lead to accidents.
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Old 7th Sep 2020, 22:04
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Average SEP 65/70 knots ...end of.
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Old 7th Sep 2020, 22:35
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Originally Posted by 3wheels View Post
Average SEP 65/70 knots ...end of.
If I approach at this speed in my SEP, I will usually go through the far hedge unless I have the good sense to go around and try again at the correct approach speed for my aircraft (around 50 knots).
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Old 7th Sep 2020, 23:38
  #27 (permalink)  
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Average SEP 65/70 knots ...end of
Yeah, I suppose that would be a fair average of the different SEP types I fly. However, there are only a couple I would actually approach at that speed, others would be faster, or slower, in accordance with the POH recommended speed.

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Old 8th Sep 2020, 00:18
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Originally Posted by BeechcraftPilot View Post
I'd like to talk about light twins in this situation. We should consider speeds like Vmca during all phases, including approach and landing. Don't you guys think that can be a dangerous approach with less speed than published?
Vmca is not a concern during the final phase of approach and landing, once one has committed to land. The Vmca published for a light twin (FAR 23 twin) is based on one engine at takeoff power and the other one inoperative. During the final phase of approach and landing in a typical light twin, each engine is only producing about 25 to 30% of rated power. Should one fail, the other only needs to be increased to 50 to 60% of rated power.

In real world operations, if you are 5 mile back on the ILS, you are almost always above Vmca, so it's not a concern. At one mile from the threshold, when you start slowing down to Vref, you are generally committed to landing, hence there is no possibility that you would need to apply 100% power to the operative engine in the event of an engine failure.

My comments are based on thousands of hours in a 12,500 pound twin turboprop, but I think the same concepts would apply to most light twin engine aircraft.
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Old 8th Sep 2020, 00:24
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Originally Posted by Pilot DAR View Post
Yes, I agree, noting that this requirement is for a latest FAR Par 23 certified plane, but is not a requirement for a CAR 3 or older 23.1581. CAR 3.777 makes no mention of IAS/CAS. CAR 3.778(a) also makes no mention, though points you to 3.757, which refers to TAS (just add to the confusion, I suppose!). 23.1581 does not seem to mention IAS until revision 23-50 of 1996. So any plane certified prior to that would not have to comply.
PilotDAR is correct. When I rewrote the AFM for the Series 300 Twin Otter in 2012, I converted and published all the airspeeds in IAS. Because that aircraft was originally certified as a CAR 3 aircraft, AFM speeds had been given in CAS since original certification in the 1960s. So, in this particular case, it was a 'courtesy' (common sense is what I would call it) to publish the speeds in IAS - legally, I could have continued to use the original CAS speeds.
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Old 8th Sep 2020, 14:15
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Thanks for the answer! I fly a Baron 58 and your comment describes exactly what we do. Since the main purpose of this topic is to talk about speed management regarding weight, the first thing that I was thinking was about Vmca.

We always follow the speed published by the manufacturer, the difference is the % of power we use to maintain the approach speed. Basically, the approach speed will be the same, with less or more weight. - Talking about light twins.

As an example, Flight Safety recommends flying base leg with 110 KIAS (Baron G58, visual approach). The Vref is 95 KIAS and Vmca 84 KIAS. The MTOW is 5,500 lbs.
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Old 8th Sep 2020, 18:28
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"Average SEP 65/70 knots ...end of.
If I approach at this speed in my SEP, I will usually go through the far hedge unless I have the good sense to go around and try again at the correct approach speed for my aircraft (around 50 knots.)"
​​​​​​Can the approach speed in a low-inertia aircraft be too high, provided the "at threshold" speed is achieved? It can be too low.
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Old 8th Sep 2020, 19:22
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Well Mouraigh1, as the saying goes "it's only the last nanometer that matters" but, this is much too easy to say. Most accidents/incidents come about because of an unforeseen event culminating in a distraction and pilot overload. Sod's law tells us that Sod is always around just waiting for his moment to strike. For the most part poorly applied approaches more often than not do not lead to an accident but that is usually down to fortune: i.e. Sod being pre-occupied elsewhere. If you follow 'Murphy's law Sod won't always be elsewhere. I suggest you take a look at James Reason's 'Swiss Cheese Model'. It is worth a google.

A stable well flown approach will always maximise the cognitive reserve to enable the pilots to deal with the unexpected and thus avoid the slips and errors which are always a major ingredient of accidents.
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Old 8th Sep 2020, 20:32
  #33 (permalink)  
 
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The POH /AFM are usually the best source for numbers .
The difference between IAS ,CAS and TAS in GA are so small that it is really and truly Academic.

A-Question may arise as to “when “you might choose to use a speed other than flight tested and approved by the sky gods .
Gusty conditions and Cross winds you might want to add some airspeed to give a little bit more control .
Aircraft might be damaged and it starts to do weird stuff when you slow down . I had the top corner of a windscreen depart in a spin . The slowest speed I could get and still have pitch control was 90 KIAS , so I landed at 90 . I was surprised how quickly it stopped on the ground . I was expecting to go off the end . But the drag from the big hole slowed the plane in under 2000 feet .
Changes were made to a few aircraft window seals after that flight .

General rule is you never want to be slower than the POH recommended speeds .I flew with a guy who used really slow speeds for short fields , but you would never deliberately land somewhere that was so short you could not get out again . Almost a helicopter approach . I Showed him how to land a 172 in 150 of ground . It was fun but the slightest turbulence and it would have got expensive real quick . Pointless exercise as you need at least three times that to get into ground effect for departure in a light plane into wind .

Many students get the airspeed covered in the circuit to prove that the airplane can be flown without the airspeed indicator working , you just have to give yourself more room and do not rush the approach .

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Old 9th Sep 2020, 01:05
  #34 (permalink)  
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The difference between IAS ,CAS and TAS in GA are so small that it is really and truly Academic.
The difference between IAS and CAS at the approach or stall speed in some GA types can be as much as 9 knots. That's not "small", and worth consideration.
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Old 9th Sep 2020, 01:54
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I try to keep it simple when training other pilots . I just use KIAS when I am sat in the aircraft .
I am not trying to dumb it down too much just not trying to reduce workload and keep it simple .
At the end of the day the indicated airspeed is the easiest number to use . Most of the trainers I have flown the differences was usually less than the thickness of the airspeed indicator needle above 60 kias.
Although it is possible to land a Cessna 152 with no airspeed indicated , fun demo for other instructors , I have rarely demonstrated students that because once they are in ground effect the dials can be a distraction and at that point it is better to pay attention to flying the aircraft .

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Old 9th Sep 2020, 02:47
  #36 (permalink)  
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Most of the trainers I have flown the differences was usually less than the thickness of the airspeed indicator needle above 60 kias.
Yes, that's my experience too, though the IAS/CAS error increases to as much as 6KIAS below 60 for the 152, a big needle width. I agree that the student will not be flying to that, but they should be conversant with it. The IAS/CAS difference should not be dismissed. On other types (some C 206) it can be as much as 14 MIAS at the stall, and the pilot should be aware of the importance of the difference. This is particularly true of Cessnas with STOL kits installed, which are common for privately owned ones, and not common for flying schools. Instructors should assure that pilots who may transition without additional familiarization training are aware of this factor....
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Old 9th Sep 2020, 03:32
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When I was checking new Mooney pilots for insurance checks , the difference between normal cruise and Va was interesting .
The Piper Meriden had quite a difference between normal cruise and Va . Both popular private aircraft .
Both aircraft had over forty knots to lose if you got into rough air or it could make life uncomfortable in the Mooney , in the early Piper Meriden the wings would fold . The FAA issued an Ad and got it fixed .
Most Aircraft get uncomfortable above Va in rough air and I only recommend flying above Va or Vb if you like to scare yourself , scare your passengers or you enjoy cleaning vomit out of airplane ceilings and carpets . Or like wrinkles in your aircraft skin to match your wrinkles ?
I am always close to Va if I am near Strato fractus ,big winds or near mountains , just a personal preference . People never remember the extra minutes the flight takes , but they will remember the scarey bumps if you do not respect Va .
The old Cessna airspeed indicators used to have a yellow arc . Top of the arc if you were heavy , bottom of the arc if you were light made Va simple .
i do not understand why they stopped painting the yellow arc on the airspeed indicators . How expensive is yellow paint ?
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Old 9th Sep 2020, 09:18
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Originally Posted by fitliker View Post
The old Cessna airspeed indicators used to have a yellow arc . Top of the arc if you were heavy , bottom of the arc if you were light made Va simple .
i do not understand why they stopped painting the yellow arc on the airspeed indicators . How expensive is yellow paint ?
Be careful with any conclusions. It might be on purpose. For example there is a difference in the white arc area. For some engines on the Cessna's the white arc goes all the way down to 0. For some it doesn't. This is related to the mandatory or optional use of the carburator heating for lycoming engines. Something similar might apply to the yellow arc (no idea what though).
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Old 9th Sep 2020, 11:26
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Originally Posted by fitliker View Post
The old Cessna airspeed indicators used to have a yellow arc . Top of the arc if you were heavy , bottom of the arc if you were light made Va simple...i do not understand why they stopped painting the yellow arc on the airspeed indicators . How expensive is yellow paint ?
'They' have not stopped. The top of the yellow arc is Vne (aka upper redline speed). The bottom of the yellow arc is Vno. Va is different to bottom of the yellow arc. The coloured arcs have been standardised and required by the regulations since 1945.
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Old 9th Sep 2020, 11:32
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The old Cessna airspeed indicators used to have a yellow arc . Top of the arc if you were heavy , bottom of the arc if you were light made Va simple .
i do not understand why they stopped painting the yellow arc on the airspeed indicators .
The yellow arc on some airspeed indicators is not necessarily related to Va. Va will generally be slower than the bottom of the yellow arc. Va is the maximum speed at which the pilot could overstress the plane with large pitch control inputs. Slower than that speed, a large control input would result in a stall, which would automatically unload the stress on the wings. Va is not normally marked on the airspeed indicator, but rather placarded, as it varies by weight.

The beginning of yellow arc on the airspeed indicator is the maximum structural cruising speed (Vno). Faster than that speed, a prescribed gust (by design standard) could overstress the plane without pilot input. Hence the limitation that flight at speeds in the yellow arc be conducted with caution in smooth air only (meaning avoid turbulent air, and don't handle the controls roughly).

The top of the yellow arc is Vne, it is certain that at Vne, you are well above Va at any weight, so you should already be being very gentle on the controls.

For some engines on the Cessna's the white arc goes all the way down to 0. For some it doesn't.
I'm not aware of a white arc on any engine instruments. The white arc on the airspeed indicator is the flap speed limitations, and will extend from full flaps stall speed (IAS usually) to the maximum full flaps extended limiting speed. There may be a green arc on the tachometer, which on most shows the normal operating range for the engine (cruise data provided), though I agree that I have seen some tachometers which at marked green from the maximim RPM (red line) back to zero RPM, I don't know the logic of this. A few Lycoming powered plane with certain props also have a yellow arc within the greed arc, nothing to do with airspeed, it's a propeller vibration caution.
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