# 737 CSFF vs Standard Deviation

The clearest difference is price: Standard Deviation at Free against 737 CSFF's $2.99. Standard Deviation also leads on iOS requirement (13.0 vs 17.6). 737 CSFF's advantage is chart position (#197 vs unranked). On update cadence, ads, in-app purchases and device support there is nothing between them.

Standard Deviation is free to download; 737 CSFF costs $2.99 up front. Neither carries in-app purchases, so what you see is what you pay.

737 CSFF ships an update every 4 months, Standard Deviation every 2 months. The most recent releases landed on August 3, 2026 and September 12, 2026 respectively.

## The numbers

| Metric | 737 CSFF | Standard Deviation |
| --- | --- | --- |
| Price | $2.99 | **Free** |
| Rating | **[5.0 (2 ratings)](https://appshunter.io/ios/app/737-csff/id1551516212/reviews)** | — |
| Number of ratings | **2** | — |
| In-app purchases | No | No |
| Ads | No | No |
| Update frequency | Every 4 months | **Every 2 months** |
| Monetization | Paid | — |
| Best chart rank | **#197** | — |
| Size | 11 MB | 21 MB |
| Requires iOS | 17.6 | **13.0** |
| Devices | iPhone, iPad, Apple Watch | **iPhone, iPad, iPod, Mac** |
| Age rating | 4+ | 4+ |
| Developer | [Dan O'Leary](https://appshunter.io/developer/1177083778) | [Ahmad Sattar](https://appshunter.io/developer/1458483953) |

## What reviewers say

### 737 CSFF

[App page](https://appshunter.io/ios/app/737-csff/id1551516212)

**Currently charting:** #197 Top Paid · Utilities (US App Store)

A visual guide to understanding Cold Soaked Fuel Frost (CSFF) on 737 aircraft wings. It references airline handbooks and Boeing FCOM guidance for educational purposes.

**Highlights:** Visual representation of CSFF scenarios, Study guide for 737 wing frost, References North American Airline Flight Handbook, Includes Boeing FCOM guidance, Educational tool for pilots

**In-app purchases:** none


### Standard Deviation

[App page](https://appshunter.io/ios/app/standard-deviation-calculator/id6444146244)

**In-app purchases:** none


## Frequently asked questions

### Is 737 CSFF free?

737 CSFF costs $2.99, with no in-app purchases.

### Is Standard Deviation free?

Standard Deviation is free to download, with no in-app purchases.

### Do 737 CSFF or Standard Deviation have ads?

Neither 737 CSFF nor Standard Deviation shows ads.

### Which is updated more often, 737 CSFF or Standard Deviation?

737 CSFF ships an update every 4 months, and Standard Deviation every 2 months. Most recently, 737 CSFF was updated on August 3, 2026 and Standard Deviation on September 12, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*